From your description of the pin-outs on the Becker, you'll definitely need an addition adaptor to utilise Sony's auxilliary input interface. That said, if Becker offer an optional lead, then there's no real need to go down the Sony route anyway.

Having had a chance to think this all over a bit though, I'd definitely say that method 2 is the one to go for. At the end of the day, you're only really going to be using the Becker as a backup, and a means by which to listen to the radio. Running the Empeg direct to the amps means you'll get a higher signal level at the amp's input, and should mean a better end result in terms of sound quality. I'd expect you to be able to run the Becker into the Empeg's aux input without any problems, and if you do encounter any, then Hugo should be able to tell you about a quick fix.

The only slight downpoint is that you won't have music in the car without the Empeg. Go for running the Empeg into the Becker, and you'd be able to use the Becker regardless of whether the Empeg's with you or not. The only time I can see this being a real benefit is when you're not going to be able to lug the Empeg around with you, and you'd have to leave it locked somewhere in the car. But then do you ever park the Boxster anywhere where theft's likely to be a risk anyway?

Dominic

Cambridge Car Audio
http://www.cambscaraudio.co.uk