06 suburban stock, aftermarket radio?

Hey all...

I've got a customer who wants to keep his stock headunit (because it's got nav) and wants an aftermarket double din Alpine unit to do absolutely everything else.

My question is, is there an aftermarket piece that will allow this alpine unit to utilize his stock xm radio ontop of everything else? His entire system is going to be amplified so I can handle the wiring of the aftermarket radio keeping it isolated from the stock headunit. I'm thinking all i would have to do for the stock unit, is keep the stock amp in there and connect a small speaker to the front left output of the amp and hide the speaker.

Any ideas?

Thanks in advance,

Nick

Nobody?

Can't believe no one has attempted this before?... I know it's uncommon... but some of you gurus have to be able to shed some info on this?

Thanks in advance,

Nick