Fm Modulator For Sc430 Levinson System

[Defuria]

I had a car stero outfit install an FM modulator and switch to accommodate an XM receiver and iPod Jack. It "functions" but sounds like crap. Can anyone recommend a brand or method for this solution without degrading the sound quality in a 2003 Levinson SC430 system?

[1990LS400]

Products from http://www.vaistech.com/ seem to be the aftermarket industry standard for adding sat radio and iPod interfaces to Lexus vehicles.