If you don't plan on overclocking, there is no reason to run anything above the stock fan, unless heat is a concern in your room. If you decide to go with the heat sink, you don't need any additional hardware outside of what comes with the motherboard. The cooler should cause an issue with your memory, as the first slot closests to the CPU isn't filled on your motherboard. I would recommend installing your memory first before the heat sink any way you go.
As for the PSU... I'm all for the Corsair 850HX. It is one of the best PSU on the market.
As for your GPU situation, I would go with a single 5870 or CF over a 5970. The 5970 just isn't worth it in my opinion. As for Nvidia, there is only one choice worth it in my opinion for your build... a SLI setup of EVGA GTX 460 SC EE. It out performs both the 5870 and GTX 480 at similar or less price (this option if you are going with a single 5870).
Thanks for the well thought out complete answers to my questions.
I reading about the fan noise from the GTX 460's which concerns me. I presently have a 9800GX2 which is quiet.
I am really confused about going EVGA GTX 460 SLI vs 5870 now and then adding another 5870 several months later. Which would be my best option for overall performance, and future proofing GTX 460 sli VS 5870 CF? I usually keep my computer fo about four years.
Going with a single 5870 now and adding an additional one down the road is more "future proof" way to go.
With going GTX 460 SLI, you have already maxed out your GPU potential and the only way to increase is get two new cards (or one more powerful/expensive card). With a single 5870, you are getting similar performance but in a few months or so when price drop, you can add an additional card for even greater performance than the SLI setup.
Thanks. I just read the article and it talked about problems with cross fire and drivers. I'm just trying to build for the first time and I'm not looking for problems that I can't fix. I'm really concerned after reading the article about doing either CF or Sli. Am I more worried than I should be? It says that one card performs well with less problems.
The GTX 460 are good cards and great in SLI, if it were a choice between a 5850 and a GTX 460 with plans to SLI/XFire later I would go GTX 460 because of SLI scaling better.
However, the 5870 is in a league ahead of the 5850 and I would stick with that choice and XFire at a later date when you feel its needed.
Of course, having said that, I've not seen any benchmarks of the GTX 460 SLI vs CF 5870 but I would assume the 5870 CF wins, but then again at a premium price.