It's a standard ATX case, and a lot of modification would be needed when it comes to replacing the ATX backplane with some solution to accomodate the Amiga ports. That's a lot of work, and to do it right you'll need good sheet metal skills at the very least. As you can imagine, the port setup on an amiga is completely different. Of course, you could always get out the dremel tool or sawzall, hack a giant hole in the back of the PC case, two way tape an A1200 mobo to the bottom of the case and call it "good", which I've also seen, and find to be an abhorrent solution.
If you are going to go through that much work to roll your own, I'd at least start with a more attractive ATX case to begin with, not something that looks like it fell out of a Compaq truck circa 1996.
Good write up on a similar DIY solution here, one of the nicer conversions I've seen.
http://www.amibay.com/showthread.php?9670-Amiga-A1200-Tower-Project
