I just finished installing it on my iBook...
My iBook is by far inferior to your PCs:
1Ghz G4 Processor (about the same as a 1.5Ghz)
768 Megs of RAM
ATI Radeon 9200 32 Meg.
Now, it runs A LOT nicer on my PC. Nevertheless, with the graphics options turned down, my little 1Ghz laptop w/ only 32 megs of VRAM plays it pretty smoothly, and it's definitely playable.
Now, of course it's a Mac (I.e. superior system infrastructure) but if it can run it, any 1Ghz+ P3+ w/ any decent video card can run it.