I have a 2007 with the bose, there are no RCA connections at the head unit. The line level signal(pre-amp) is available, I cut the end off of an interconnect and soldered in to the stock harness. The only problem is the door chimes come through according to the gain setting on the amp which could be very loud. I will be switching to the rear signal shortly to prevent this.
Good Luck the wiring diagram is stickied here on this site so you know which wires to connect to.