Actually, you can fit an A4000D motherboard inside a Baby-AT case, I did it myself (with the 7-slot busboard). The A4000D motherboard is relatively small so you do not have to mess around with the PSU typically.
The problem when hacking A4000D into a small case is that the turbo is going to hit the internal 3.5" bays. So you either cut them off or run it with the 030 soldered onto the motherboard. Thats why it is a good idea to get a wide case, as said above.
