I have had XM in my car for over a year now and have been quite satisfied with the sound quality (even though it is connected to the sound system via an FM modulator) and overall performance (eg, it is easy to reach to the ashtray and change stations, the antenna is totally unobstrusive, etc.). My unit is an Alpine, but I would guess that the the Roady or Commander, being newer, are as good or better. Never having had Sirius, I can't compare their programming with XM's, but I find XM great and a vast improvement over standard FM radio. I think it is clearly worth the money to get XM. I have no criticism of those who have paid more and, in some cases, had to overcome various obstacles to get Sirius, but I am personally not attracted to that approach.