Ya, go for the Nforce 4 SLI board. Then if you want to upgrade to 2 graphics cards in SLI mode you'll have the upgrade path. Don't worry about having two x16 PCI-e slots, none of the graphics cards today can even use the bandwidth in x8 PCI-e. So the mobo's with 2 x8 graphics slots are fine.

Check to see what two 74GB raptors will cost vs. the three drives you have on you list now. Raptors are sweet drives.

Make sure you get a case with a drive bay cooling fan if you're going to run those 10,000rpm drives. Preferably with 120mm fan in front. Cooling is going to be key with a lot of this hardware, and you don't want a case that's going to restrict air flow.

Power supply. Minimum I'd go with is 480Watts. Enermax is good, I haven't had any complaints about Antec either. Top of the line (and will set you back $$$) is PC Power and Cooling, Inc.

Other than that, have fun.

Edit: Wish I could get a G7 but I'm left handed and they're right handed only. Razor's are nice. If I had a choice I'd go with the G5 or G7 myself.