Thanks for this guide, very informative and well-organized.

I do have 2 questions though:
1) I've checked out 3 PSU wattage calculators - eXtreme, Newegg, and automatic PSU calculator on CyberPowerPC.com when using a build customiser. For a build with i5 2500k CPU and GeForce GTX 570 SLI GPU the results were varied, but I'm particularly worried about the results NewEgg calculator showed me:
eXtreme: ~750w
CyberPower: 700w
NewEgg: ~880w
So I'm wondering if NewEgg's results are valid or completely absurd. :S
2) This is the PSU I'm getting:
COUGAR SX850
It's on sale with a nice discount if I buy it in a combo with GTX 570. Customer reviews are nice so far, and so is a more thorough
professional review. However this is an unheard of brand and isn't even mentioned in your guide. I'd be curious to hear your opinion on this PSU.