> I would love to see some benchmarks to compare different cpu.
> Maybe there are some websites that have them from within OSX ?

Some benchmarks including PowerMac G4 results in various configurations:

http://www.barefeats.com/g4up2.html
http://www.barefeats.com/kwik.html
http://www.barefeats.com/g4up.html
http://www.barefeats.com/mini01.html
http://www.barefeats.com/pb11.html
http://www.barefeats.com/pvp.html
http://www.barefeats.com/g5sum.html
http://www.barefeats.com/pm07.html