The easiest way and a way that takes less room is to put SBC (Single Board Computer) in a BIG BOX AMIGA. In one board you can have the whole computer, minus the sound card in most cases. I have seen them in 386, 486 and Pentium flavors.
I modified my A2000 so I can have more 16 bit ISA slots here
http://eab.abime.net/hardware-mods/6...a2000-sbc.html
I had a 486DX2 50MHz one, which felt a little to slow when playing Doom on it, I would say it was comparable to 25-33MHz 68040 on my A4000. I'm pretty sure 386 would be to slow to play Doom, but it would be nice to see comparison to 68030 at the same speed.