Sirius XM Radio Starbase SC-FM1 Satellite

I've had my Starbase for almost one month and am considering on returning it. It's a beautiful unit, installs easily and is intuitive to use. I use the RF modulator on my existing factory car stereo. Normally, my native radio reception and sound quality is excellent. When I hooked up the Starbase, all the higher frequencies clip (distort) which is very noticeable especially from the right channel for some reason. I've phoned Sirius and they sent me an antenna wire so that I could eliminate the RF modulator, but it still does the same thing. If I use native FM or play CDs, the sound quality is perfect. I'm going to hunt for a better Sirius receiver. Hopefully the broadcast quality from Sirius is not to blame. It's a shame too, I really love the look of the Starbase.