I made my harness tonight - turns out Radio Shack had 18 gauge speaker wire pre-wired with RCA ends...one RCA per speaker channel with positive and negative wires on the opposite end. Exactly what we need! This made soldering and taping my connections a snap, which was a good things since I haven't soldered anything in 10+ years!!
Here are pics of the harness - since the cable from Radio Shack is all sold separately in the same color, I used tape to mark the connections. Full solid black is the rear, stripped is front. The RCA with tape on it is the right channel, no tape is the left.