Couple of myths and caveats of building a gaming rig, just so you know.
SLI - is a waste of money, your video card will be obsolete in 6 months or less. If you always want to be cutting edge, it is best to just get 1 high end card every 6 months to a year, rather than run SLI. Parallel processing mode, is nice with data throughput at times, but its not a constant better performance. You may benchmark higher, but real world performance in game, one 8800 versus 2x 8800s side by side comparison, you wouldn't really notice a difference.
RAID 0 - does nothing for games, makes your system less stable and higher prone to crashing. You lose one drive, your whole array fails. Buy one high end top speed hard drive for performance. Like a Raptor.
4 gigs of RAM - probably overkill, but RAM is not super expensive. So maxing it out wouldn't be a huge waste of money. If you run Vista, and load a video game, I doubt you would ever get close to maxing out that 4gig of RAM. If you did, that game is very poorly coded. Also, overclocked RAM, is a myth and a marketing scheme. RAM is pretty much RAM. I used to work for a systems builder and Microsoft reseller back in the day. I used to build gaming rigs for people who liked to blow $4,000 on a gaming rig. I saw all kinds of stability issues with over clocked RAM, which is why I'll never touch the stuff. Again, it may benchmark higher, but it doesn't perform any better in real time.
My advice to you is to get a decent processor, you don't need top end. A lot of crunching will be done by your gaming video card. So, like a quad core, 6600 or whatever from intel be fine, probably more than fine. Decent motherboard. I typically use Asus, because I have been using them for over a decade with little to no issues at all. Abit is good and I also have a MSI board that has treated me well. This comes down to some personal preference. If you go AMD, get a board with a VIA chipset, they tend to rock with AMD systems. Get one high end gaming card, this will be the bread and butter of your system. The new video cards are slated to come out after new years sometime (first quarter 08). You may want to hold off till then if you want the top of the line.
Power supplies, I typically only buy Antec. Been using them for over 10years with no issues. I never had an Antec go bad on me yet. I hear people give them some shaky reviews online now, but then again some people complain about dumb things in my opinion. Like the main power cable is too long? Ever hear of a zip tie?
Are you looking to build this or buy it?