A lot of people (including myself) have been complaining that Aperture has unnecessarily strict hardware requirements. Well, it seems the Aperture Compatibility Checker may provide some hints as to how to ease some of these restrictions:
The above is the result I get with my modified Compatibility Checker on my fully supported iMac (20" G5 2.0 GHz, Radeon 9600 128 MB, OS X Tiger 10.4.3, 1.5 GB RAM).
More fun with the Aperture Compatibility Checker. :)