the next logical step ...
1. Make PowerBooks G5
2. Make iBooks G4
3. Make Xserves G5
that way ... the iMac, eMac and iBook (consumer) are all G4 .... and the PM, PB and Xserve (pro) are all G5 ...
and there have been two versions of "white" iBook ... first with clear covers (white paint on inside) and silver (aluminium) handrest ... the second has solid white covers and a white handrest (plastic???)