XLR8 today introduced a 550MHz G4 upgrade for Apple’s “Sawtooth” Power Mac G4 systems. XLR8 is providing the upgrade to owners as part of its “Trade-In/Trade-Up” program; customers can send XLR8 their current processor and receive the 550MHz upgrade for US$299, or they can agree to a send in their current processor after they receive the upgrade. The latter option requires placing an extra $300 deposit that will be refunded when the original processor is received.