Well since She who must be feared and obeyed tends to hog the Intel iMac, I bought a (very) cheap g4 800 from 2002 for my photo retouching and to learn how to build missions (I was allowed a $NZ300 budget

)
I thought it wouldn't run SF1918 since the minimum spec on many sites had said 'g4 1gig' ; but it runs just fine! Mind you I have bumped the ram to 1.25 but it's still got the crappy 32mb video card - it gets a bit jerky on missions with lots of moving elements (same with SF1945) but still playable.
I bought an apple 17" lcd (also dead cheap) at the same time with the old powered adc connector so I'll have to hunt a bit for a replacement 64/128 video card - ah well, next year.
Total cost; pMac $NZ100
display $NZ 100
mouse and kboard $NZ30
extra ram $NZ20
Total $NZ250 about $US170 (including freight costs)
Old tech sure,but they're easy to work on,still run plenty of software and look great (Apple's best design period imho).
Anyway just thought I'd share; and if you're looking for a spare mac they're a great choice.
Cheers!
R.