I use a a1200 with a 68020/4meg accelerator. I find that this is enough for perfect playback of like 99% of the games i have. The only problems i have is some old certain games like oil imperium or newer fps games which runs a bit too slow due to lack of cpu power.
By the way.. has anyone gotten oil imperium to work using whdload? The problem here is that the drilling part of the game runs at least 5 times faster and there is some severe graphic corruption.