AirFlyer, you consider an 8600 as a "lower end video card"? Heck, I'll take one any day. Check this out though. I have a 7600 256mb and 2 gigs of RAM. With 48-50 processes running, I run AH with hi res and all graphics sliders to full and always have a steady 75 fps, which is my screen refresh rate. I have an AMD 5000+ dual core processer(s), about 2 years old. I really think AH just runs differently on everyone's machine. I know peeps with half the processes running and newer vid cards that get 20-30 less fps than what I get. Not bragging, I consider myself lucky, as my old system, no matter what I upgraded, would only get 20-40 fps max. I just think each machine is its own beast.
Don't mind that AirFlyer guy, he is spoiled by his GeForce 8800.

I still laugh that my 7900GS runs so well with every game I own, although I do plan to upgrade to a 9800GTX/GTX+ in a few months.
I take my 7900 over an 8600 anyday, When I bought it, it was said to perform better than the 8600 aside from Shaders.