Don,
I have the Kenwood KVT 915 with Sirius and a Roady XT hard wired into the auxiliary port of the 915. I have an JL amped system with twin JL 10" subs and amped Alpine component door speakers. I find the XM sound tinny on talk and music "swirly" (my technical word). I suppose SQ is in the ear of the beholder and is somewhat subjective. I have spent a lot time fine tuning the 915 to give me the sound that I like. I do constantly adjust the bass with a rheostat controller. I listen to everything from Rap to Classical to talk and find the adjustable bass very handy.