I didn't tried Quake on my new BPPC, i can't help you, but i want to say something about frame rate and games, obviously a game with a refresh of 50 fps will be smoother, but i know commercial 3d games that runs at 25-30 fps.
To Laser: did you have a PSP? did you played to GTA Liberty City Stories? i have a PSP and GTA, the game runs at 25-30 fps, and it works very nice, very playable, from my point of view, i think that 25-30 fps are the minimum frame rate to be playable, although 50 fps are the best to play a game.