I ran HL2 on my PC and got tolerable performance:
AMD 64 3000+
1GB PC3200 (clocked to 2700 because my mobo is a pos)
XFX 6600GT
I played HL2 at 1600x1200 and it was pretty good MOST of the time. I used 4xAA and 2xAF, with all of the settings on max, except for "Reflect World" instead of "Reflect All." I would get from 60-130FPS indoors, and about 40-90FPS outside.
To be honest, unless you have an LCD that must play at that resolution, you would be better off playing at a lower resolution. If you play @ 1280x1024 it looks really nice, and your FPS will definately go up. If you are concerned about getting amazing framerates as opposed to the performance😀ollar ratio, then just get a 6800GT or 6800 Ultra, you would be much happier.
It is very playable on the 6600GT, but it is much better @ a slightly lower resolution.