I'll be the first to confess that I'm not the best on electronics, especially on computerized vehicles, and that the wiring of the premium sound system and how sound is transmitted from the radio to the speakers is a bit of a mystery to me but here is what I can offer:
1. I asked about boosting volume because stoutdog's right front speaker occasionally would not produce any sound unless he "goosed" the volume at which point it would work fine. However, the dash mounted tweeter and the rear speaker on that side worked fine.
2. the premium sound system has 2 amps that are physically mounted on a bracket attached to the left and right front speakers inside the door. Stupid design and further complicated by the fact that, while the amp is held in place by 2 torx bolts, that neither the front speaker nor the amp is available as a separate unit (e.g. you can only obtain an amp/speaker replacement as a single unit - ca. $160 from a dealer and ca. $100 via
http://car-part.com/ although I suspect you could do better at a local auto salvage yard). The amps serve as a "choke" point in the speaker system, as I understand it, in the sense that the signal is routed to the amp from the radio and from there to the 2 door speakers on that side and via a crossover the "high" signals are sent to the dash tweeter. Hence I'd speculate, given that you have no sound on that side, that a) there is no signal to that side from the radio either because of a radio problem or a wiring problem or b) the amp is dead hence no signal to the speakers on that side.
3. there is a rather large multi-wire plug going to the amp that may be loose, although it does have a catch lock that should be engaged. I presume there is someway to test whether there is a signal coming out of the radio and going to that plug but I cannot offer any advise on how to do the test.
The amps are encased in a solid block of what appears to be resin with some heat sink fins and shouldn't die but I suppose it is possible. The more common problem with those speakers is the "surround" foam goes bad in which case you can go online and get a foam surround repair kit or you can replace the speakers like I did per
viewtopic.php?f=45&t=73768 . If the amp is bad but you do have a sound signal from the radio head to the amp I'd lean toward dumping the factory system and getting a new head unit from like Crutchfield along with new door speakers (I suspect but don't know that you can splice into the existing factory harness for new speakers) but that will leave your dash mounted tweeters not working unless, way out of my league, you add an aftermarket amp/crossover. If you have no single between the head unit and the amp you are on your own to look for a wire break.
Hope this helps at least a little bit.
PS - hexus he says he has the stock 6 CD head unit (RBQ) with the premium (6 speaker) sound system which is the same unit I have and the amps are in the door on the speaker. FYI that's the same amp arrangement that's on stoutdog's 06 with the OEM remote CD changer. As far as I know all the OEM premium speaker systems are setup the same way regardless of the radio head unit. IIRC there is a bit of an amp in the head unit but the premium sound system has the speaker mounted unit to serve as a cross over and an amp to drive the premium speakers.