If you are looking at picking up a machine for MorphOS, might I advise something that has it's own Video card as opposed to a built in Video chip that uses Shared RAM.
I don't understand why exactly, but MorphOS and it's programs expect a LOT of Graphics RAM and will not default to the Fast Ram (unless I'm missing something).
In my case I'm running MorphOS on an eMac and I had to turn a lot of the extra features off just to be able to use my Web Browser, not to mention multi-task.