Assuming that the CD player doesn't have any controls on it and is controlled through the stock head unit, there's not much you can do with it right now. A few people have talked about trying to figure out the protocol used to control such CD players, but no one has actually succeeded, AFAIK.

On the off chance that that CD player has its own controls and it has RCA line-level outputs (or something that could be converted to RCA line-level outputs), then you could hook it up to the empeg's aux inputs. However, I'd say that the chances that that's the way that player is are next to nil.