If you really need a system now, just get your stuff, as they are good choices...your mobo is a bit much unless you really want to utilize SLI at full 16x, which quite honestly isnt all that better than dual 8x (but i wouldnt mind having that mobo :laugh: ). The premium and deluxe from Asus are good choices too.
Theres all this talk about waiting for AM2, but even when it does come out this summer, I highly doubt that it'll be cheap like the 939 hardware right now, so itll be even more months perhaps of waiting after that...and besides wouldn't you want the AM2 to mature a bit before jumping into something entirely new? When you do decide going AM2, there will be a lot more better and cheaper chips available for it than what was released at launch. And as everyone has stated, please get 2 gigs of ram (those OCZ Platinum are great, might check out the Golds too or even the PC4000 Platinums), games like FEAR will probably cause some bottleneck issues.
Everything in your wanted rig looks fine, you should be using that sytem for quite some time with maybe a video card upgrade being the earliest upgrade down the road.
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AMD X2 4400+ Toledo
XFX and LeadTek 7800 GTX 450/1250 in SLi
DFI Lanparty nF4 SLi-DR (704-2bta BIOS)
2X1GB OCZ Platinum DDR Ram (2-3-2-5)
Hitachi Deskstar SATAII HD 250 GB
OCZ PowerStream 600W SLi-Ready Version
NZXT Guardian Case
Creative Sound Blaster Audigy2 ZS
Creative Inspire P7800 7.1 Surround System
Samsung 204b Black 20.1" LCD (1600x1200)