The A1200 form factor is pretty unique and you can do a lot with the case as it is. 120 gig 2.5" IDE drives are easy to get and you can also easily run off of a CompactFlash card with an adapter. If I were you, I wouldn't tower it unless you were thinking of getting an expansion slot backplane.
I built my A1200 into a 1U rackmount case because I was using it as a full time server, but I did enjoy the A1200 form factor when it was in the original case. A 60 MHz m68060 with 80 megs of memory and an internal 4 gig SCSI hard drive was kick ass in 1995.
The modifications took a lot of work, but the machine's been 100% stable in the 1U:
http://lilith.ziaspace.com/
