I did have one installed in my previous Subaru Impreza. In my current Impreza I've installed a cheap JVC headunit and am relying on Bluetooth from my iPhone to provide music.

I do in theory have an easy install to add an empeg, there is a spare slot under the JVC headunit that has a cubbyhole at the moment. Hopefully one day I get round to installing it. I do have the amp I used for the install in my previous Impreza, though I imagine this time I'd probably just use the aux in on the JVC.

I'll not be bother to try and install one in the Passat, far too much of a hassle.