Several concerns in regards to upgrading the stock system:

1) Has anyone installed subwoofers in the trunk? A quick search revealed nothing. I'm particularly curious on people's opinion/experience on putting a single 15" sub in a ~ 4 c.ft box in the trunk.

2) Am I correct that the front door speakers are 6.5"? Is there a stock tweeter location?

3) Am I correct that the stock sub location in the rear deck will accommodate a 8" driver?

4) Has anyone looked into having an aftermarket usb iPod connector installed in the factory headunit? Given that it is a factory option I can't imagine this isn't possible.

Sorry for all the questions.. I have not yet taken delivery of my 09 A4 premium package and am anxious to have some of these questions answered.