ok, one of the main reasons to go with x48 is for crossfire. If you want to do that, you have to get AMD/ATI cards. If you're going to stick with one Nvidia card, just get a P35 that costs WAY less and performs just as good.
if you want to do multiple GPUs, and still want the 9800gtx, you have to get an Nvidia chipset, like 780i
those hard drives are pretty much old tech by now. they have pretty good access times, but are loud, expensive, and small in capacity. Make things easier on yourself and get a 750gig or terabyte drive. they are fast and store a crapload of stuff.
i have a rosewill PSU (850w on sale $45), and it's fine, but everyone will tell you to get a better brand, and justifiably so, as a crappy PSU can cause big problems. your call on that one.
finally, you can probably save a little cash by getting pc26400 ram. Good quality RAM will oc to 8500 levels anyway and cost less because of marketing.
conclusion: save $ on the board, hard drive, and memory. put it toward better psu. take what's left, give it to me
edit: hey, I'm an enthusiast now. Hooray for me! I'd like to take this time to thank me for doing all the work.