Plain A1200???

[doctorq]

Parts needed for building an A1200 into a tower...

-Motherboard (I think you would need a PAL motherboard, if you plan on connecting it to a TV)
-Keyboard adaptor
-Keyboard that works with the keyboard adaptor
-Floppy drive with front blend
-Floppy cable
-Tower with enough space and a PSU (the most easy PSU to mod is an AT PSU)

Nothing more, nothing less. The IDEfix you mention would be good to purchase as well, for connecting up to 4 devices to the IDE controller, and an accelerator for adding fast ram and getting more speed.

[doctorq]

You might be able to make a case for the A1200 keyboard, but buying a keyboard adaptor would make it easier and most likely also cheaper.

Floppy isn't compulsory, but what would you do if your harddrive fails? You can of course just have an external drive laying around to connect in case it happens. Personally I prefer to have the floppy installed in the tower, but people are of course different.