I have an '06 package #3 with the standard sound system. It's mediocre, at best. The biggest problem is the treble, which is very weak. I have to crank up the treble to maximum to get much of anything, and the two back speakers are useless in the higher frequencies. The JBL system has to be better (doesn't it)? Does anyone make aftermarket speakers for this car?
A wonderful discussion of encoding formats but... I can't compare it to the standard audio system, but I have to say I'm a little disappointed in the JBL Premium audio system in the 06 Prius. I have had premium systems in other cars, such as the Bose system in my Audi, and I find the JBL system just doesn't measure up. The bass is weak and lacking. The midrange is boomy and muddy. The lack of a true subwoofer hurts the system on both counts. Overall, it just isn't a premium system.