you can install a aftermarket cd player w/ the monsoon. You just have to tie into the stock amp turn on from the aftermarket head unit, and a few other things. I wrote a write up on it a lil' while ago, I am a lil' busy right now, but will post a link so.

You can use the stock gps antenna for the avic, but it requires a a lil' bit of electronics experience. It is just easier to put the new antenna in.

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Steven Oliver
2004 GTP comp-g WS6. Gator and suede all around interior.
Advanced MECP certified installer, custom upholsterer.