I haven't done a great deal of searching, but have looked around a little. I have the CTS-V with factory nav and want to replace the head unit. I know about using the PAC interface harness, Metra dash kit, and antenna adaptor, but since some of the convenience features of the car are built-in to the OEM head unit, will all of that stuff still work?

Also, I'd be replacing entire Bose system, so what size speakers are in the front and rear doors?

If the head unit can't be replaced, I'll add a USA-Spec iPod interface, and would like to just use the head unit as a pre-amp to an aftermarket 5-channel amp for front/rear/sub (all aftermarket stuff).

Any suggestions?

You need to hook up with a professional installer either in here, at a GM dealership, or a GOOD sound shop.

If your car is anything like the later Seville/Deville line with Bose systems, the head unit is actually part of the serial data bus and TheftLock system and the car's VIN (Vehicle Identification Number) is programmed into it. Improper aftermarket installs have opened a Pandora's box of electrical and theft problems in these cars.

Thanks for the advice, but I actually own a shop in my town. I'm a dealer for several different brands including Peripheral and PAC, but I wanted to see what everyone else has done because I've honestly never worked on one of these cars. PAC lists a databus interface, and Metra has a good kit, but like I said, I just want to see what everyone else has done or general advice.