Had my first A1200 in modern times and my first expansion was a Blizzard 1220 (020@28Mhz and 4 MB Fastram). It already is a real fine and noticeable boost. I was really surprised how much from the speed-up doesn't come from the cpu but just from having some fastram.
Now I have an Aca1233 (030@40 and more Fastram that I need) and I really like it. Not only because it makes the system faster but also it needs nearly no power (AFAIK <4 W) and thus doesnt need active cooling or get hot. From
watt what I know about other 030 cards it is +- a few Watts the same. So for me it's the sweet spot too.