I always loved the A2000 for the space inside (and I'm decking one out right now).
My A1200 always suffered due to lack of Zorro slots and even after fitting one into a tower case I hated the cludge-like add-ons, held on with tie-wraps like the Power Flyer Gold IDE adapter.
My A3000 was a big disappointment due to the restricted case size (and lack of AGA).
Finally I went for an A4000 which gives you just enough room to cram in almost everything you need (RTG, USB, DVD, Fast IDE, etc). The last move was to add a Mediator board which involved transferring it to a tower case. At least I no longer have to fold, prod, bend and force cables into tight spaces.
Go for the A4000.
