Which G4 iBook to buy?

[anonymouse1]

In the wake of the water spill into my wife's iBook, I'm looking at buying a used G4 iBook. I'm looking to spend as little as possible, certainly no more than $500 (any more than that and I might as well buy a Macbook).

So I'm wondering if there's any "sweet spot" before which it doesn't make sense to buy a G4 iBook--is there some point at which the bus speed goes up, video card changes, etc. Are there any models that are known dogs, to avoid?

Thanks!