You can run os3.9 on a2000 with some turbo card. I tried to run on my a500 (kick 3.1, 68030/14MHz, 5.5MB ram). It runs, but its performance is very slooow. I dropped some programs, because lack of memory, but the main bottleneck is the ecs gfx. With a "modern" gfx card it will run fine i think.
Anyway avarage speed of Os 3.1 with 640*256*16 color on my a500 is about the same with os3.9 on my ppc/68040/33MHz with 1024*768*16bit, voodoo3.
