Sorry, I wasn't trying to shoot down anyone's ideas. It's just a lot simplier to use a PIC chip (see my previous post) to fool the sony unilink bus into thinking there's another device on the bus thus enabling the aux-in jacks. The hard work is already done and no hacking on the empeg is required. The PIC chip's code is open, so you can have fun with it if you like. The PIC chip already supports a serial port, so you can figure out how to control the empeg from your sony headunit too if that interests you. Myself, the sony headunit is only for NPR and the four local college radio stations; that's it. YMMV.
Cheers!