The most supported powerful system is the PowerMac G5 bi Pro 2,7 Ghz (this is the one I own).

I have also a Mac Mini 1,5 Ghz and a PowerBook 17" 1,67 Ghz.

MorphOS really flies with the G5 (ok, Wayfarer sometimes struggles to display some pages but it's waaaay faster than on my G4 system, thanks to a more faster FSB and of course faster CPU speed).

I have had the chance to find one with the original Radeon 9650 with 256MB RAM, fully supported by MorphOS with 2 DVI connectors.

I also wanted to try Mac OS X Leopard on this system and, that surprised me, it is really efficient with the dual CPU used for everything. The system is almost as snappier as MorphOS (but with way more productivity software).

I've just bought a PowerMac G5 Quad that I have to test (waiting for the right electric cord) and I think I will use it with Leopard to let the G5 2,7Ghs be used only with MorphOS.

I wish that one day MorphOS could use (in a way or another) some kind of SMP, even on PowerPC.