Good luck, otherwise contact phoenixconsole.
Easy to build a desktop or tower so long as it has 3 pci or 2pci ports and one agp/pcie video slot so you can be sure to use compatible sound, video and network cards. (Soundblaster live emu10k, nvida supported video, and intel/100 network cards)
Mini pc's usually have less slots. (More problems) If I wanted a mini pc to run aros, I'd go to phoenixconsole or hmmm... an imica.
If you really want to do this, support those guys, because they can give you an out of the box machine for cheap and save you tons of headaches and heartaches...
Steven