Do you really need 6GB of ram, or a 2GB 4870? Look for a cheaper 4 gig kit. And please dont get that video card, it offers no improvements over the 1gb 4870. If you're willing to spend that much on a video card, then get the 4890 instead.
I agree with xthekidx on the motherboard as well. I would go with the gigabyte am3 790x or 790fx, they have 2 slots and much better value.
I am assuming you want the Phenom 955 because you want the best of the best; it is nothing more than a 'feel good' upgrade. But if so, then i wouldn't blame you. But if you were looking for value, you should get a cheaper quad, or a triple, and just overclock.
The 3x RAM kits are for i7; he'll just need a 2x kit for a PII.
Noise comes from fans. High RPMs come from heat. Heat comes from power (used, or especially wasted). Consider the games he wants to play when selecting the video card. Will a 4670 cut it? A 4870? Then find one that is quiet. I like the IceQ4 Turbo models from HIS. They exhaust their heat, and the fan is very quiet. I've got their 4850 in my primary PC, and am about to install a 4670 in the other.
Overclocking increases bang for buck, but also increases heat, thus noise.
Make sure the PSU you select is 80+ certified. If you over-size it a little, it will run especially coolly. My system probably pulls only 350W from a 650W PSU, so it stays inaudible, even though it has an 80mm fan.
The budget is somewhere under 2k, he is an average computer user and wants to play games once in a while. He is the type of guy who just wants the best, he said he wants to reward himself and finally get a awesome computer.
I will persuade him to go i7, so I will keep the corsair memory
I was originally going with the 4870 because he wanted hdmi, but i let him know dvi will serve him just fine so its 1gb 4890 now.
I think the PSU will be quiet and still have room for xfire in the future.
There are some GPUs that are either passive cooling or have aftermarket type coolers that can be very quiet. The Western Digital Caviar Black series are faster hard drives then the "blue" series, but they're also a bit noisier.