Remember to take into account what you're going to get out of building a more powerful Amiga. What do you expect to run on it, and will you really use it?
Most of the stuff I run on my 060/Mediator system ran just fine on my old 030/AGA system. It basically exists as a glorified mp3 hifi these days.
If you've got a bit of spare cash; what the hell go for it, it'll be a laugh, but remember you could probably get quite a nice quad core x64 system for the same money ...
