For one, skip SLI. SLI is a waste of money. 1 killer 8800GT video card would be all you need for 90% of games. And if you decide that you really want SLI, then get both cards now. Because if you get 1 now, and later on you decide to get another one, you find that newer cards have come out that are faster than 2 of your cards combined.
Water cooling is for people that overclock their systems. If you are not going to be doing that, then a standard air cooled system will be fine.
XP will not technically play DX10 games in DX10 mode. They will play them in DX9. But there are a couple of games that you can hack and make them play in the high settings of DX10. You really need Vista for DX10.
No you do not need a 64bit system to SLI. 32 bit runs it very well.
And just a warning. Cyberpower has only a C rating from the Better Business Bureau.
http://www.labbb.org/BBBWeb/Forms/Bu...anyID=13080817
"Complainants allege the company sells defective merchandise, and fails to provide warranty service as agreed. Some complainants allege they receive merchandise which is inoperable or defective at the time of delivery. In other cases customers complain they return defective components two or three times for the same repair, or, repaired items are retuned without the repairs performed, in the same condition as when they were sent in for repair. Complainants are generally dissatisfied with the level of customer service provided, claiming they are unable to reach company personnel by phone, and e-mails are not responded to. Some complainants who request refunds on defective products are dissatisfied with the company's policy of deducting S & H charges from the refund amount."