It seems there's not a lot of information on the web about upgrading the stereo system in these cars. Until recently there were really no options other than tapping into existing after amp wires to do anything. However I thought I'd share some part numbers and descriptors to help you guys out who may be looking. And make some suggestions, fair warning though, any stereo upgrading will be costly because of the unique devices needed to make it sound good. so here it goes.
To those who want to upgrade the stereo head unit they do now make a kit for our cars, Locating one on the other hand will be tough as they are not available online as you will have to go to a local car audio shop to order one, same goes for amp bypass wiring.
You can view the kits available by going to Metra Online | Welcome to Metra Auto Parts Online Warehouse
and simply punch in your year and model of car.
I personally have the bose centerpoint system, and actually really like the scrolling up screen so keeping the head unit stock is cool with me. So in my situation, I wanted to upgrade the mids highs and add bass. Go with the metra kit, AX-DSP-MOST1, this bypasses the factory amplifier all together and gives you RCA's to plug amps into. It also comes with a dsp (digital signal processor) so you can do time alignment and a nice EQ for tweeking the mids and highs.
I just requested to order one of these so in the mean time i tapped into the woofers in the trunk and used that for bass signal to run my subs. I used an audio control LC7i line driver adaptor to convert to RCA'S and it works like a charm (considering im using an amplified line)
JUST MAKE SURE if you go this route, that you are getting a Bass signal off the speakers you are tapping, the rear deck speakers i found to be the best for this. However there are 2 sets of wires running into these stock rear deck speakers, you need to tap into the bottom wires, the top ones produce mids/high sound and you wont get any good bass from there.
I ran a 1/0 awg wire OFC (OXYGEN FREE COPPER) for powering my amplifier, (rockford fosgate 2500 bd cp), Powering 2-t1 12" subs, the car sounds great with just this upgrade alone
I also made a power remote turn on wire for my line driver and amp, you can tap into the fuse panel on the left side of the steering wheel located behind the little compartment door, I used a 'mini fuse circuit tap' and was able to pull an ac turn on wire from there.
Most all of the factory tapping stuff, other than the remote on wire, is in the trunk, if you need to locate the factory amplifier, its on the passenger side behind the carpet, all the way against the body wall, its silver, and has a green plug and black plug into it. I have tested these lines and have found out what they are, i have a diagram too if someone wants it.
Hope this helps