I have looked at this for a little while now and I think I might go this route
http://www.crutchfield.com/S-mY6XmaEm3qJ/cgi-bin/ProdVi...?g=226950&I=108DP1US
Everything I have read sounds good and you can hook it up wiht an FM modulator that actualy plugs into your antana plug in the back of the unit. This will eliminate interference, and it also has an additional aux imput for anything else (XM)