The better your reproduction hardware, the better a good quality source will sound.
I've connected XM radio to my 950 setup -- though I ordinarily use it in my office -- and was quite pleased with the sound.
Yes, you could get by with less, but then you'd want to upgrade later anyway. Especially if you get into a house.
The 950 will give you excellent performance right now with the XM Radio and also offer lots of room for expansion later.
[This message has been edited by boblinds (edited July 20, 2004).]