why not just run a 3.5mm iphone jack that splits into RCA jacks, plug into the amp and control the volume and songs through your mp3 player? all you have is a audio jack wire to plug in. Not much to it, cheap, and not tempting to steal. Thats my plan when I get to that point. Marine 5-1/4" speakers in the dash, a 2channel 40 watt amp, and an aux audio jack in the dash. Set the amp volume at the highest level that you would typically want, then adjust down from there. If you have the amp already, you are in it for $10 bucks. At least it makes a good temporary setup. Make a nice Jeep playlist and let it go!