Unfortunately, you're throttled by the bus speed - only 66 Mhz on a beige G3, 100 Mhz on a B&W. A 1 Ghz upgrade will certainly improve things, but it won't give you the same performance as a new 1 Ghz G4. I'd prefer to spend my money on an actual G4 - a Sawtooth is under $1000 around here these days. Then, later on, spend your next whack of cash on a 1 GHz upgrade for the Sawtooth - upgrades will be cheaper by then, anyway, right? (I know that the Sawtooth still has a 100 Mhz bus, but the whole motherboard architecture is superior, and don't forget the AGP!)
Cheers :-> Bill