WIth regard to satellite radio sound quality.
The current state of satellite radio sound quality is really awful. Music channels are completely unlistenable, and the better your audio system is, the more it reveals the defects and compression artifacts. The spoken-word channels have even more compression applied and sound awful as well, but at least you can tolerate that when listening to talk or news. If you love Sirius, there is no need to upgrade your speakers or the rest of the audio system... it might sound worse.
Comparatively speaking, Sirius sounds FAR worse than a decent FM station (HD-Radio or otherwise), far worse than an iTunes download and far worse than a reasonably made MP3.Pandora, MOG and Slacker Internet Radio sound waaaaaay better than SIrius, too... and they're all compressed (just not as badly).
There is no technological reason why the sound quality could not be excellent. Sirius/XM has the ability to determine how much data bandwidth they give each channel, so if they wanted to you could have near CD audio quality on any given channel. The unfortunate fact, however, is that they have chosen to allocate very little bandwidth to each channel in order to be able to offer more channels of programming. So, they apply tons of "proprietary compression algorithms" to squeeze the data. It sounds bad on purpose. It is not a high-fidelity service, which is a real shame because it has the potential to sound great, if people could live with half the number of stations.