I have a couple IIx machines and I like them. I snagged mine over a decade ago and recapped them before the leaks caused any real damage. I also have a Daystar adapter in one of mine, so that's fun to play with.
Does the RAM clear the metal drive tray? I forget how much room you have.
I have a...
You best bet is to use an external supply like the kinds used in mini or micro PC's and then make a custom board in the empty PS case to make any special voltages you need and connect that to the old wiring harness.
The 6100 supplies are not long enough for a server type removable ATX supply.
The 81/110 needs the PS removed to get to a lot of stuff and isn't that fun to unscrew actually. The case is painted metal except for the front faceplate (cosmetic with removable metal backing), so it won't fall apart anytime soon.
The only time a heavily upgraded machine is worth more than the sum of its parts is when it is a one of kind machine with unobtanium parts.
Building a computer is like working on a car, your labor is free, and the customer gets the parts you paid full price for at a major discount (not worth it).
Yea, a bit of an overreaction sorry.
I just don't think they run that hot unless you are overclocking them or using a chip that has been relabeled for a higher speed. A simple heatsink with minimal airflow is good enough to keep you from getting burned.