AROS + UAE is not a friendly path to travel as of yet.
Amithlon would be my first vote though you may have to tinker for a while until you learn to understand how to set up your hardware. It ain't hard, but at first it seems like it.
My second vote would be for the WinUAE machine using MircorXP, but again you are going to be held back not only by Windows, but also by WinUAE's short comings, like OctaMED S.S. not working as it should, where as you can just run OctaMED S.S. native in Amithlon.
I feel ya, my 2000 mobo is dead, I tried to find someone to fix it for me, but no one was willing, so I tried my self, but to no avail. Pisses me off. :/