Thread: Can I integrate with Mustang Shaker 500?

They are correct.

The high end integrated stereo systems are made to work in unison. The impedences of the speakers is different from those in the aftermarket. The amplifiers are made to work with those impedence levels, and the head units are all funky as well. The amplifiers have crossovers built into them. And generally each set of speakers has it's one amplifier (one for tweets, one for mids, one for subs).
You will have to completely part with your 'high end' stock system if you want to put in any of your aftermarket stuff.

A lot of times, the stock speakers are at 2 ohms. if you were to hook those up to an aftermarket radio, you'll smoke the radio. If you hook up aftermarket speakers (4 ohm) you 1) won't get near the output, 2) will be messing with the way the system was set-up to work in unison, thus chances are it will sound like crap (what with the crossover points being set for a different set of speakers and what not).

As for the subs in the doors, I don't know because I haven't seen the new stangs inside, torn apart yet.