What sort of performance are you getting, and how playable is it across those systems?
For all intents & purposes, 60 fps should be considered the max, as its a programmed limit.
Computers I have tried it on:
AMD Phenom II x6 1090T OC @ 3.94Ghz (more recently at 4.05Ghz) w/ stock evga 460 2win (2x 460 in SLi on a single card) - windows 7, 95%+ idle, 60fps(1080p) (This is my workstation I use for 3d modelling & rendering; I also tend to play my more graphic & cpu intensive games on here too - it auto UC's to 900mhz when cpus are under low load): Overkill. Pure and simple. Even the most ludicrously epic battles are playable, with gratuitous amounts of ships.
i5 2410m (2 cores, 4 threads) @ 2.3Ghz w/ integrated intel HD3000 - windows 7, 60-30% idle, at least ~60fps (have not tried intense battles - this is a laptop I recently got as a gift) (1366x768): Definitly playable, though it has limited headroom for background multitasking. I need to test heavy battles later.
AMD Turion x2 @ 2.1Ghz w/ unknown nvidia mobile graphics - windows vista, 5-30% idle, ~15-45fps (depending on intensity of battle) (1600x900?): Playable in missions like 'turning the tables', but large battles like 'holding the line' are truly painful
celeron 743 @ 1.3Ghz w/ integrated intel express 4 - windows 7, 1-5% idle, ~8fps (1366x768): Nigh unplayable. Even the menus lag. Max framerate is ~13fps when starting a battle with one ship, engines not thrusting.
For reference, they are listed here in the following benchmark:
https://docs.google.com/spreadsheet/ccc?key=0AiqfhgzyU7crdHVHZ3lsY1R4eElhY0FheXJnNExPaFE&hl=en_US#gid=0 <-- chart
http://www.neurohack.com/transcendence/forums/viewtopic.php?f=6&t=4332 <-- benchmark
Interestingly, all but the turion (Which I have not yet tested) have managed to get above-average passmark scores for their cpu's
(1090T scoring over 8000 on an unstable OC (over 2000 above avg: ~+33% increase), i5 scoring 3500 or something (it was 200 above avg:~+6% increase), celeron scoring 514 (only one I remember exactly) (~100-200 above avg ~+25-60% increase)