Looks like a Mac Mini G4 alongside an Amiga 1200 would be my best choice then? Funny, I used to have a PowerBook G4 Titanium that might have been acceptable for MorphOS, but that fell victim to a rather notorious hinge defect in those macs.
No, the Titanium PowerBook is not one of the few supported models. Only the last four 1.67GHz G4 PowerBooks will be supported (and one or two 1.5GHz models, but they must be a certain revision, so you must be very sure you are getting the right model).
There are 6 more of the 1.5GHz G4 MacMini's for auction with a "Buy-it-Now" price of $175.99 on eBay right now, which is a very good price. Check the other thread I posted about them in the Amiga Marketplace forum.