Upgrade Dilema: 8800 GT or new CPU/Mobo/RAM

Current System Specs:
X2 3800+
Abit AN8 32X
2GB DDR3200
2x GeForce 6600(SLi)
24" Dell LCD

Games I wanna play:
The Witcher
Bioshock
Neverwinter Nights 2 - MOB
Assassins Creed (when released)

My question:
Given what I have and what I want to do which component in my system represents the biggest bottleneck? I'm thinking it's prolly the GPUs but wanted some outside opinions. I'm also looking at this in terms of future games (like Assassins Creed and others). I think for now I want to be able to play NWN2-MOB and The Witcher at fairly high res 1600x1200+ w/mostly everything everything turned on and run at a brisk FPS. Would this be viable with the my current system specs sans old 6600 + 8800 GT? Or would it be better to bite the bullet and upgrade everything? Any help appreciated!
thnx yall-

Forgot too mention that it's a 939 mobo as well which significantly limits what CPU I can upgrade too (basically the only viable chip for the price @ socket 939 = x2 4200). Would the move from 3800+ to 4200+ make that much of a differnece in regards to the before mentioned games?

The 8800GT or the HD3870 would really be your choice of upgrade. CPU/Mobo/Ram is for faster system loading times and it will improve FPS a bit, but the key is your video card (even if bottlenecked by your cpu), a faster gpu is more significant than faster ram and cpu in the games you want to play.

go with the video card upgrade, it'd make the biggest difference

thnx all-

I dont think that upgrading from the 3800 to the 4200 would make enough of a difference to warrant the cost, instead overclock your current cpu a little.

I would get the video card, either the 8800gt or 3870 and then when that system isnt playing games at the resolution that you want it to, then i would get a whole new rig.

Actually it appears that newegg is sold out of the 3870 as well - in one day i might add. Next best thing (after 5min of looking) is @ TigerDirect for $259. Supply and demand can be a real SOB sometimes
cheers all-