Erwylh

XFX TS Bronze 430W is a bad idea, is an outsourced (so not manufactured by Seasonic, just designed) as well as XT series. They are basically Seasonic Eco rebrand. In my country it has an exceptionally high rma ratio (>30%), however, XFX TS 450W and higher modells are great choice.

2x6pin can take 150W together plus 75W PCIe. Guess what, its impossible to draw more than 225W, therefore 280W TDP is false. Theorically however you can punch the standard on the face (see 295x2) to reach 475W power consumption if you really want to burn those cables. So 600W is fine (if you are not that wicked) but you take huge risk with CX or TR2.

I consider them "dangerous" PSUs.

Since PSUs are designed to bring their rated wattage reliably, you don't get any benefit for stacking up unused watts and since you don't plan to apply SLI configuration, you are perfectly fine with 550. To quote Linus, your wallet will be more empty than ever, needlessly. So you can pick an even higher quality model that has lower wattage rating for the same price or you can save 40 bucks by buying the smallest of the same series. Obviously Pure Power is not designed for OC systems (has the same platform as EVGA B600) which means it is recommended to swap it out. However, before chosing your PSU consider making plans about your future updates (sli or smth) to get the one that fits your desired PC the most.

Neither S12II nor 6100 is designed for OC systems, and I don't consider 700MHz difference a bit of overclocking. I don't even think you can get to 4GHz at all without a high-end mobo.

You mean never. Nobody should buy "only peak" psus, this is the first sign of dangerous models. So its irrelevant to consider stacking up wattage that we don't use since if you buy PSU from a trused manufacturer, you can see the continous wattage and you should watch review from every model before buying it. But I am not sure you understood my problem, let me quote again, I wanted to point out this one: This is not true, there is no relationship between the two things. Anyway, good PSUs last long enough to survive many builds so I don't actually understand why do you focus on it's lifespan instead of other components. The main problem is that ppl are usually on tight budget (let's say 100$ or sometimes under 60$ as OP ran out of it aswell) so if your system's max consumption is around 250W then you are perfectly fine with a great ~350W-400W model (e.g. Seasonic G360). OR you can say you need "moar watts" and you will buy Corsair CX750 for the same price - which is obviously worse. And your configuration may blow up because you sacrificed quality for unused wattage. Okay, my example is extreme and wasnt about this build but I hope you understand extra watts are expensive so you should calculate your needs properly if you can't afford a better one since you pay more for nothing (or less).

This is not true.

ECO gives you more wattage @ 12V (396V vs 360V). However, its fan is "loud" (compared to s12II), has lower life expentancy, shorter warranty and somewhat less stable.

Well, not if you lose quality to gain "headroom". Corsair VS 350W is as bad as Corsair VS 650W except the latter is more expensive for nothing. TDP ≠ Max Power Consumption so both calculation are false.

What did your friend do exactly?

You have to find the ideal performance/price ratio. First: This is really cheap setup, you have to search for used stuff (but I noticed you do). Second: you don't actually need an HD6870 for 1440*900 (overkill) thus I recommend to get something similar (or weaker) but more energy efficient (e.g. GTX750). Third: You shouldn't trust any PSU model without professional review and there is a reason why your PSU doesn't have any PCIe stuff. Look, the PSU is the most important thing in any build, everything is powered by it. So if you decide to save some money then you're gonna have a bad time. Maybe it doesn't have any safety certifications that means a lightning strike will light up your house... and will be burnt down to ashes. Or maybe it just doesn't have good voltage regulation - this damages your components in short term (= your caps on your mobo and videocard will blow up, dataloss on HDD etc). Guess what, nobody knows. Obviously.

You don't need more than 550W with any single gpu solution therefore 550 G2 is far better for you.

You can buy fanless from 125$...

You should pick i5-4690k instead (same gaming performance, much cheaper) so you can pick a better board.

Both have to be on 230V.