I just upgraded my speakers to my GT w/out premium sound (no external amp) to Infinity References in the front and Infinity 6 1/2 in the rear. I'm thinking of upgrading my HU to the 05 Camry Navigation System. (OEMvalue.com) This requires me to install the JBL factory amp (220 watts) (according to OEMvalue.com) or an after market amp. My question is this, how does the factory amp compare to an after market (220 watt) amp? The factory amp comes in a package deal w/ the Navigation system for about $1700. If I were to buy an after market amp in addition to the Navigation kit, it would probably be an additional $300-$400 (wiring kit, amp & installation) is the extra money really worth it, considering I do have Infinity speakers?