The old G4 733 is slightly faster than the new G4 733, as it has a 1MB L3 cache. If you can find an old one for cheap, get it instead. Note that the day before the new 733 was announced @ $1699, the old one was selling for $2,999. Prices on them, where they remain unsold, must have dropped however.
Also worth noting is the fact that you can "dumb down" an 867 system to $1,999 pretty easily. But that is higher than you were looking to spend.