What's the best thing to upgrade in a PC with $150?

I'd recommend a Radeon HD 7850 for around 139.99
it'd be worthwhile to wait for 179.99 for a Radeon HD 7870.

Radeon HD 7870 is currently ranked at #21 Performance rating(4252)
Radeon HD 7850 is currently ranked at #30 Performance rating(3712)

Depends on what your current PSU outputs in addition to what you plan to upgrade. If you plan to get a new GPU (which would be suggested) then a PSU would certainly be suggested before the GPU.

Do you think upgrading my power supply should be a top priority?

The power supply is the only thing that can damage everything in your machine if it fails. When they do fail, they usually fry at least the motherboard. If you're unlucky, the motherboard will fry your CPU as a result, along with your RAM.

Powered graphics cards and harddisks that are plugged into the power supply are usually also killed as a result.

It's really up to you if you want to take the chance of overloading your PSU if it's not rated for what you're trying to pull from it.

As I and others have said, it all depends.

If you have a 500watt power supply now, you "should" be able to get a video card in the 150 to 200 dollar range and be fine.

But anything lower then that and you should get a new power supply.

A good brand name power supply should run you 60 to 130 dollars depending on the brand and type and size you get.

I picked my Corsair TX750 after doing a lot of looking around. It was on sale for 80 dollars during xmas a few years ago. The main thing that sold me over other slightly cheaper ones was the fact that it could be in a room that 50c degrees. Now that don't sound like much, but where I live I have seen the Temp get up to 42c with a feels like of 47c. Most other power supplies are only good up to 40c room temp. At this lower temp the power supply wold have a harder time keeping itself cool which is part of what causes the damage and a lower life span.

It also has a 5 year warranty on it, which is again more then most other power supplies out there.

Today if I was to buy a new one, I would be willing to spend a little extra to get a modular power supply. This way I could add in just the cables I need and keep the rest outside of my case for a cleaner look and better airflow.

There is one other thing you might want to consider. A UPS, an Uninterpretable Power Supply. In case you don't know what it is, its a battery in a box that you plug your system into and plug that into the wall. They are great for brownouts, blackouts, power dips, buildings with old wiring. Any of those things can also kill your system. The larger it is the more time you have to shut down your system to protect it. I have a 1500VA system which gives me about 20 to 25 minutes real time to shut my system down.

If your area has the occasional brownout or blackout, or you notice your lights dimming now and then you should consider getting one if you don't have one.

Then it should be a new power supply. A new power supply will also get you through future system upgrades.

Then a new video card. Again this should last through a number of system upgrades. Also when looking at video cards, look at the physical space inside the case. Some of these newer video cards need 9, 10 or even 11 inches from the back of the case to the front.

If you have DDR3 ram, then this should be your next consideration. Look at how much each slot on your motherboard can take. Some motherboards are limited to 2 gig sticks, some 4 gig sticks, some 8 gig sticks. If your motherboard can only take 2gig sticks, then it should be time to consider a new motherboard. If it can take upto 8 gig sticks then you shouldn't need to replace your motherboard for a while and should upgrade your ram.

Last should be CPU and motherboard that is if your motherboard can handle more ram. You should see if your motherboard can handle a newer CPU. If you can't put on a newer quadcore cpu on your current motherboard, then you should consider getting a new motherboard. Replacing a motherboard and CPU at the time can be expensive. But at least its not as bad as what I had to do. I needed an upgrade, but my ram and cpu would not work on a newer motherboard so I had to buy a new motherboard, cpu and ram all at once. That set me back nearly 600 dollars cause I also had to pick up a new blu-ray drive because the motherboard I picked out did not have ATA connectors, just SATA connectors, which is good, but annoying. I could have gone with just a DVD drive, but heck I wanted to be able to play blu-rays.

I know its a lot of info, it can take time to wade through it all and consider everything. The path I suggested is pretty much the one I took. I went, Power Supply, video card, case. All those items could be upgraded independent of CPU, motherboard and ram. Then after I was happy with all those things, I saved up for the big upgrade which I had to do all at once which was my CPU, motherboard and ram. I did them all at once cause there is no reason for any of the parts to be sitting around for months at a time being unused, not knowing if they work or not.

Depends on what GPU, some of the newer are very power hungry.
Depending on what the GPU says it requires you should tack on 200 to 300 more watt again so you have wiggle room.

In my system I also have up to 5 extra hard drives plugged in. Having the extra wattage is nice when I need it.

And again as I said, when you are not running your power supply near its max all the time till help its life span.

My thoughts exactly.

Beg to differ on the SSD point.

For the majority of games, I would agree with you, but there are games where it will help.

My girlfriend used to play a lot of WoW, and she had the install on her SSD, logging in and moving to zones was pretty much instant. There was no waiting for anything to load on screen, and she was always the first into an area running about.
I didn't think it'd be so much of an boost since I thought her machine was pretty fast anyway loading in WoW, but even things light flights were silky smooth when coming into cities and such.

Then, there is games with a huge amount of content, such as Sims 3. Another game she put on the SSD, and load times with all the expansions went some stupid-go-get-a-coffee-while-it-loads to less then 30 seconds. Worlds loaded pretty fast and there was no re-draw or load time when panning the worlds, or following the taxi service.

I'm sure there are loads of different games that'd have a speed increase from a SSD, maybe not in FPS, but that's not what everyone wants or needs to enjoy their game more.

It got patched to 4 now.

Which you don't.

I wouldn't say it's more than enough, unless you want to close all windows before playing this gen's games. It is the minimum requirement.

SSD probably won't give you more FPS, but they can make a game run smoother and more enjoyable.

i have seen the difference between a SSD and a HD load times.. trust me if you start using a SSD, HD will feel ancient to you.

Storage is less i understand but you wouldn't have these moments if you use a SSD.

I always recommend a SSD for the operating system and a few programs, sure it's not necessary but they do increase over all performance.

Hell yes everyone needs one!!!!! :p
I see your point but it's not like he even has a decent spinner.
Which is more underpowered a GTS 450 or a 200 GB spinner, bet it can't even do 50 MB/s sequential read.
But yeah if he can find a great deal go GPU I just don't think $150 will get him that much more GPU.

No, he didn't, 4GBs of ram is still adequate, and an SSD will boost program's start up and loading times, as well as windows boots (mine takes anywhere from 21 to 40 seconds.)

So no SSD cache and no USB 3.

I'd suggest using at $10 of that money for a USB 3 card. I got one off eBay for my HTPC and it works well. Even my external USB 2 drive runs faster with it.

Given that you're using a 200GB drive and external USB 2 drives I'd say that a disk upgrade would make a significant different to everyday use.

Still, given the budget I think that you have to decide what's more important to you, high resolution / quality games, or more everyday usability. A graphics card is an obvious update, I'd suggest a Radeon 7850, which can be had for $140 (less if you consider rebates) or GeForce 650 Ti Boost if you prefer NVIDIA (same price, and slower on most games), plus $10 for a USB 3 card. For everyday use, another 4GB of RAM plus a larger internal disk.