For the motherboard I would, personally, go with the DFI nForce4 board.
RAM, well, yeah... 1GB really DOES make a HUGE difference in modern games. HL2 on max settings stutters like crazy with only 512MB. You will need 1GB of RAM. I would suggest some Patriot PC3200 with XBL or G.Skill RAM, they're both TCCD with the Brainpower PCB
I've got 1GB of Patriot RAM myself.
Graphics, is there a 6800NU in PCI-E? I've got a 6800NU AGP card and it's pretty good. Apparently the 6600GT falls behind when you start going in higher resolutions with AA/AF, something to think about.
Hard disk, well, they're cheap. Try and go for a 120GB drive atleast
Don't forget to get yourself a non cheapy PSU. Don't skimp on it. The PSU is one of the most overlooked parts. A few of the better brands to look for are Antec, Enermax and OCZ. If you want the best of the best, go for a PC Power and Cooling. But really, try and avoid the cheaper generic PSU's.
Reply is probably a little late, but that's my opinion
