As someone who has owned an 8 MB RAM expansion, a 40 mhz '030, a 40 mhz 6840 and a 50 mhz 68060 A1200, my opinion is that the sort of things that need speed really need a 68040 minimum to do them justice.
Whether you get 22 mhz 6820 or 28 mhz 68020 it will still annoy you, because all you still have is an '020.
If I had a stock A1200 I'd definately get fast ram for it, but unless I could get a 68040 or better, I wouldn't bother with cpu upgrades.
