As long as you have the cash, power supply and airflow for it I'd seriously reccomend nothing less than a full 68040/25 for any worthwhile experience these days.
I dunno how the prices compare any more, but the slowest full 040 you can get (25MHz) is roughly twice the speed of the fastest 030 (50MHz) for integer performance. For floating point stuff, the 040@25 is similarly a lot faster than the 68882 external FPU @ 50MHz.
An exception to the rule is floating point code compiled for 68882 that makes heavy use of trancendal maths. The only trancendal function in the 040 is the square root. The overhead of trapping and emulating unimplemented 68882 code wil pull the 040 back but there are programs that can eliminate this (OxyPatcher for one).
If you can afford it, a full 68060 crushes the 030/882 combo :-D
