I created a 10' Harness which had enough conductors to bring the speakers and power back to the RR saddlebag. I CUT the end of the Becker radio connector off and used the Clymer schematic to properly connect all of the speakers, ground, and ignition power to the harness. All splices were made with marine grade butt connectors with heat shrink seals. Some folks like to solder, but I will swear by these connections when they are done right.
The harness was by far the most time consuming item, Everything was taped first, then the harness was routed down the Left side of the bike and across just behind the rear shock adjuster. A whole lot of black ty-wraps were used!. The Sirius antenna was attached to the existing antenna bracket with a custom mount I made (the included plastic mount was too small for the base diameter of the OEM antenna).
Everything was routed to the factory CD changer hole in the saddlebag. I slightly enlarged it and used a standard rubber grommet. I later siliconed this up to make sure everything is watertight.
I mounted the amp vertically on the back wall along with the Sirius unit. This took a bunch of time to wire it all in and get the cables neatly wound up. There is some excess multiconductor cable which cannot be cut, so it just needs to be coiled up neatly.
Then I added a piece of marine construction board to cover the wires and leave some room for whatever airflow will occur. I had to make a small bracket to secure the bottom.
I still have more room than when the factory CD changer was installed.
This system works great, I have my Sirius, iPod, AM/FM, and Marine WX to boot! My only negative is that I do not have my speed sensitive volume and control at my left thumb. I suppose I will live with it!