I have an expanded Commodore Amiga 500.
I modified a PC bigtower for the A500 mainboard. And built a new backside made from 2 mm thick aluminium.
I also made a keyboard connector: it’s the 15 pin DSUB connector near the standard A500 connector row.
And it has a normal hacked ATX power supply. The long IDE cables are made by me too.

If you wanna hack a bigtower case, then you have to be sure that the mainboard really fits inside:
the A500 mainboard is really big. I had to cut away some parts from the top frame inside and
the ATX power supply is now standing vertical instead of horizontal.

Ematrix turbocard: 68030 @ 50 Mhz, FPU 68882 @ 50 Mhz, 24 MB RAM, Kickstart 3.1 (Amiga OS 3.1)
for compatibility it’s switchable to a 68000 and Kickstart 1.3!