My personal take on it is that it's kind of pointless to stick a 1200 in a tower.
I can see the benefits (more room, more expandability) but I think you lose the 'retro' feeling of the classic desktop case.
If you really want to go RTG, then just go for a boxer (my personal fav is a 3000).
If I was rich and famous, I'd probably have both an 060 based A3000 and an 030 based A1200 AGA machine.
I'd use the A3000 for RTG stuff and keep the A1200 for playing WHDLOAD games.