Supreme Commander retail has a built in benchmarking test as mentioned
here . To enable it start up the game with "/map PerfTest" after the command line (eg create a shortcut to supremecommander.exe and add /map PerfTest after the " " section in the target.)
The
lower the score the better. You can also find min/max/average FPS in the log file it produces after running.
From the the looks of that thread, resolution seems to be a big factor in performance (obviously) as are the in game settings. Running without sound also gives a huge boost, and the problems various people have mentioned seem to indicate they have some problems in that area codewise.