With an Orangebox game, the most you will actually be able to get on Windows is 500fps right now, due to Valve's 50% FPS restriction. We talk more about this here: viewtopic.php?f=44&t=5473
The cvar to set on the command-line, or in a server.cfg, would be fps_max for Orangebox games. You'll want to set it to maybe 30% higher than the actual target FPS, since the game does some strange internal rounding/adjustments. If you set fps_max on the command line, supposedly it can't be changed later.