G5 books (be it PowerBook or iBook) have not been released or even announced yet. Apple is releasing a slightly modified PowerBook in March that has a 1.67 GHz processor. But it is expected that the PowerBook G5 will be announced in June. The iBook will follow after that. I would assume by October or November. That's usually the order of things at Apple... the new Powertower, then the iMac, then the PowerBook, then the iBook, then the eMac. Since the iMac was announced last October, the PowerBook would likely be next. However, I don't know if it will fit in your $1600 budget. They tend to be a bit pricey at first. You may have better luck buying one of the G4 Titanium PowerBooks at that price.

I do recommend them, though. I have a G3 PowerBook Lombard that I have had for nearly six years now. I do need to upgrade to OSX, but I've got to find the time (and the media).