I am somewhat of an audiophile and I blamed the poor quality of the free sirius media player from their website on the fact I don't pay the extra for the 128kb stream but since having downloaded Starplayr for windows I have noticed a dramatic, in the realm of 3-5 times better sound quality from the starplayr stream over the media player link on sirius.com.
hope this helps you audiophiles and those that don't like parting with cash!
ps. Im not affiliated with starplayr, just a new fan.