Jntar you know I got your back here. I would recommend first, one of the Corsair power supplies. They are great PSU's and they are among the most stable on the market in their price range. The memory you are looking at is good, but for real gaming I would go with a step up on the XMS series at the least. Trust me you will notice the difference.
What exactly is your budget on a system right now? DO you already have the video card? Are you locked in on the case? Does noise effect your decision on that at all? I do have some very nice custom systems built around gaming starting off @ $850 right now. They are not on the site yet, but I am working on that.
If it's in your budget I would look tot he new AMD quad core processors. Motherboard and processor run about $450, but even if you simply base your motherboard off of the new AM2+ platform you are really future-proofing your system since all the new AMD processors are based on that. (Note: you can indeed buy a lesser motherboard that is AM2+ I beleive the price starts off around $70, but again if you want to futureproof your purchase in the build I'd recommend either the Asus or Gigabyte motherboars @ $200+)
Next, are you going to be using windows vista? or are you going to be using windows XP? If you are going to use Vita I recommend at least 2gb of system memory as well. If you have any other questions feel free to post here or pm me. I'd also be happy to spec out and build a system for you as well. (benefit to that being I'm certified and can warranty everything in the system for up to three years, as well as provide tech support and do so for about the same price as you would be looking at total for your system)
www.alchemy-computers.com btw to check out what I have to offer, right now again tho just my laptops are up, but I can design rigs as well by request.
-Alax