PC Build : PSU ?

Yes.

I don't think so, you will need more than that tbh.

http://www.coolermaster.com/power-supply-calculator/

This might help. :) When I was building my PC everything I read kept suggesting a PSU over 500W just to be safe even for simple systems, there's no harm going over but going under could wreck your machine.

I'm kind of disappointed that every new CPU and GPU need less and less power... My Seasonic 620w is not being utilized properly since I moved away from Core2Duo/gtx9600 combo couple of years ago.

Should be plenty, just get a reputable brand and not some generic junk.

Have similar system, I was thinking about buying 450W and everyone said its more than enough. If you think about upgrading your pc, you may think about a better PSU but for this system, it should work :)

You can get away with a smaller one, but if the price is right, it sounds like a good size. I would suggest a power supply bigger than you need for 3 reasons.

• Most power supplies are the most efficient when you are drawing around 50% of their max output. 40-60% is probably optimal in most, but some can be just as efficient outside of that range. This usually only makes a small difference though, I think around 2 to 4% worse efficiency at very high or low load.
• Using a larger power supply than you need will heat it up less and put less wear on it which will allow it to last longer. It will also be quieter because it will not run the fan as fast.
• Having a larger power supply than you need now means that if you decide to upgrade to a more power hungry card in the future, you will not need to buy a new power supply. If you buy a 300 watt PSU now and then upgrade to a card that draws 200 watts in a few years, you will need a new PSU (especially if overclocking). Also, I am not saying that this specific 450w PSU would work with a 200w GPU, it's just an example, especially since it only has a single 6 pin power for the GPU.

https://linustechtips.com/main/topic/631048-psu-tier-list-updated/

Tier 1-3 is acceptable. 450W would be just enough.

Alright, thanks for answers !