A stock A3000 with OS3.9 is great machine and very compatible with most software. A graphics card will give you many modern abilities (good looking internet, playing most video clips) but, some games stop working. Adding a 68060 or PPC will cost more compat. but open the possibility of MP3s, TVPaint and faster everything (030 is no dog though). An 030 with a MasPlayer is supposed to be pretty good for MP3s.
It all depends on what you enjoy doing!