U need to Buy a new MOBO AND CPU becuse if you buy only the CPU it will be bottlenecking ;)

What's the point in buying a 1080p monitor if you can't run any games at that resolution?

Whenever you want to (or when your current set dies) get a new CPU and mobo.

Motherboard 1st
You need good foundations to build on :)

your setup is almost as old as mine, except i'm running an underclocked 560ti and 8gb ram but i have windows on a ssd.

i have no need for a better cpu, but obviously my gpu is suffering now with new games like witcher 3 (and probably with fallout 4). i'll probably update to a newer nvidia gfx when they drop a bit in price (970 are like $550 right now...) and another ssd for games.
but that's just me. based on how much i can invest in a gaming pc, i'm not allowed to be very demanding.

I have a Phenom II 965 and an AMD HD 6850. My gaming performance is slightly under yours. Still running what I want on 1080p in the 30-45 fps range, sometimes even with high or better settings.

As for upgrades, you cannot really do much. People seem to not have noticed the crucial fact that you have an AM3 socket motherboard, not an AM3+ one.
No, they are not compatible.
The best AM3 CPUs still floating around the market are a few leftover Semprons, which are worse than your current one. Not that you could upgrade to so much better; even a Phenom II would mean a roughly 10-15% boost, and they are mostly available from dismantled PCs.

The GPU is a decent mid-range one even today. It has reached the point where office workstations start to use similar cards, but as I said, I use a worse one and still live with it comfortably.

As for changing anything:
GPUs today are PCIe 3.0, your mobo is 2.0. You'd have a GPU you cannot use to its full potential = wasted money.

CPU upgrade is impossible without motherboard too. Even with a quad-core newer gen Core i3 or an AMD FX 8000 series you's start bottlenecking at the GTX 660, rendering CPU+mobo by itself pointless.

So, in essential, I'd say live with it. Sure, that monitor is small, but that's the least of the problems. As it is, that rig can live for about 12-18 months if you don't want to play the newest stuff like Arkham Knight. In the meantime save up money for a newer one. You can get a decent gaming rig with an FX 8000 or a budget Intel (Core Pentium, the G-series CPUs) and an AMD R7 for about 450 USD. Great power can lie for gaming in the low categories, if you know how to build a good config.

I hate this good enough for 1080P gaming nonsense. There's no such thing. It's a myth incorrectly carried over from the old days when the cards with high VRAM offered you no extra performance at standard resolutions and really were only of benefit to those running much higher resolutions/multiple monitors/large custom texture packs/a lot of AA but those days are GONE. These days we have games than can top out 3GB VRAM with ease and we are desperately in need of some sort of performance breakthrough to get back ahead of that requirement.

Fact of the matter is that if your new ultra powerful GPU can max a modern game and get above 60FPS at 1080P it is NOT a waste of money. It means you've potentially bought yourself an extra year of being happy with the GPU.

Similarly if a GPU is only just getting 60 FPS in most modern games it is not some supposed sweet spot that's good enough for 1080P gaming. Because if right now it's only averaging 60 FPS, sometimes even less, then tomorrow (next year) it may well be failing to provide the performance/eye-candy settings that you desire. And I am not a fan of making investments I know will have to be replaced in short order (within a year or two) again and again and again. I like buying something that will be a faithful provider of entertainment for as many years to come as I can get.

A GTX660 is neither of those things. However that's not say it's worthless because how well it still holds up depends entirely on how happy you are with dropping the eye-candy to get back to playable frames and what you consider to be playable frames. I wouldn't be happy, but then I'm all about trying to get 1080P 60 FPS at max settings out of any GPU I buy for the next 2-3 years if it's at all possible (I currently have a GTX780, previously had a GTX260 for 5 years). Conversely though the 980 actually does not deliver 1080P at 60FPS in all circumstances, we need another jump for that to happen, so I wouldn't consider it or anything else on the market a worthy upgrade which may make me more inclined to stick with a 660 if I had one.

And the whole reason why you're getting conflicting reports is because people have different minimum standards they are willing to accept and because the GPU and CPU work in tandem and can be handicapped to less than optimum performance if the one or the other is much weaker so only upgrading one of them is not always the answer and may get you less performance than you paid for. In all likelyhood many of those that say the CPU is holding you back think that AMD processors are worthless and have a 660 or similar themselves and those that are telling you the GPU is holding you back may well be AMD fanboys. I personally think both are in need of a boost as they're both aging mid-range components and thus both are likely costing you frames VS the top-tier stuff (well a 660 hasn't really gotten that much weaker since release, game requirements just jumped a little out of reach and moved the bar up abnormally).

I'm not going to address the CPU and Mobo thing...I stopped believing in AMD as soon as the Core2 processors came out of the Intel factory, especially after all of AMDs failures to even pretend to keep up since then (although I'm told the current ones are finally acceptable). So my only advice would be to go Intel.

if you stick to AMD you can buy a mobo that will be compatible with that CPU, AND also be compatible with an 8-core FX series processor. thats what i did with mine, i had a Phenom II X4 925, with a very old mobo, bought a new mobo an Chrosshair V Formula, sticked the old Phenom in it and ran it like that for a couple of months until i had enough money for a FX8350.

If you go for intel, well its going to be procesor mobo and memory in one blow, so save up money.

the video card is not bad, it should be able to run games for at least a couple of years.

I wouldn't get too caught up in trying to hit Ultra @1080-60FPS. When pushing to that upper limit you're getting serious diminishing returns on your cost for a difference (between high and ultra) you really wont notice while actively playing. You're looking at something absurd like a Titan or SLI 980/970s plus a serious CPU upgrade (and the mobo to go with it), probably an SSD, and of course a monitor to display it.

My 660 has been serving me well @1080 but then a again I'm using it to PLAY games not watch a FPS counter or make comparison screenshots. I'd decide what you want for your CPU and then start watching for deals, particularly combos with an acceptable mobo. If you can hold out until November for black friday, or at least the next major American holiday, that's what I would do. If you save enough money you can justify getting a new monitor on sale at the same time. I'd go for a fast response 1080 over 1440 if i were in your position but take into consideration that I almost always consider budget over being on the cutting edge. There's just too many cost and issues that come with staying right at the front of tech and too many good games that are a few years old that I haven't played yet.

I was at the same 1080-1440 crossroads about 6 months ago too. Despite really wanting the 1440 I went with 1080 because I got a Samsung for $100 during black friday and the cheapest 1440s run at least $300 and that's for some unknown brand and I was hoping to string my 660 along until the 970's or better drop in price and running at 1440 would have made a GPU upgrade necessary sooner. I also think 1440 is a stopover resolution on the way to 4K (or VR). I plan to stay at 1080 until 4K or VR becomes viable and cost effective as a main display.

P.S. I would absolutely add an SSD for installing games you're currently playing. The difference for games with frequent map loading (multiplayer games) is substantial and the cost is so low.

Have you cleaned it in the past 5 years?

You've met with a terrible fate, haven't you?

Guise, suggest me specific motherboard, CPU and SSD models #PLSPLS

Thanks!