True David, the fastest non-accelerated G4 macs (other than the Powerbooks) is the 1.5 Ghz Mac Mini.
And that model has enough VRAM to make it work well with MorphOS.
Personally, I'd prefer a 1.42 MDD or an accelerated Powermac (at least until Powerbook or G5 support is introduced). Those models have more expansion options.
Whatever direction Steven chooses, he's bound to find NG systems to be more capable then legacy hardware.
I'm fond of real Amigas too, but for everyday use they're just not up to some tasks.