Asian
These are two seperate markets, the PC market is only selling >2GHz from new at the moment on x86 for a platform that runs WindowsXP variants and Linux.
The PowerPC market is running >800Mhz at the moment for MacOSX ( although you can run nicely at about half that ) and the AmigaOS4 market, when it exists, will come in at >600Mhz for new hardware.
Waiting for G5 is pointless, IMHO, AOS4 will not exploit the chip for some time to come and first we need a PPC northbridge supplied for A1 ( and in the alternative market - pegasos/morphos they have the same challenge ).
Remember, even when Amiga was at its prime, you had to treat it as a different market as far as MHz was compared.