@Helgis
I have done exactly the same, changed for the G3-XE.
The reason I originally went for the G4 was the clockspeed. This was when the G3-XE was annouced as being 700Mhz. Now it ships at the same clock speed at the G4 version.
I'll be changing to one of the dual CPU boards later. But in the meantime I think the G3 is more than adequate.
Don't forget that some users have got A1-XE(750FX) overclocked to 933Mhz. :-P :-P :-D