You can hit seriously high fps in source, with sv_cheats of course.
You are slowing the game down to an unplayable level, but it shows what it is capable of.
1. Load up a singleplayer game.
2. Console > sv_cheats 1
3. Console > host_timescale 0.01
4. Console > net_graph 3
5. Console > cl_showfps 2
My 9600GT tops around 3000. but then again the game is unplayable. Rendering my post useless.
But it's cool to see what it can really handle. Go even lower on the host_timescale, I dared not cause I wanted to play at the time, worse that can happen is a crash. I think.