I purchased a Sirius Starmate Replay over the Holidays and I must say that while I am impressed with the quality of the programming, the sound quality is pretty bad. I would equate it to listening to a 64Kbps MP3 stream, not a MP3Pro or MWA stream, but plain old MP3 at 64Kbps,
maybe 96Kbps. The high end is very muddy with quite a bit of artifacts in the encoding. Cymbals are the most affected. I really hope that Sirius will address this in the near future. My friend got an XM radio over Christmas and when he comes to my place we'll hook it up to my Stereo for a comparison. But a word to the wise, if you are expecting CD Quality, don't expect it from Sirius, near-CD quality? Nope, I'd say more like near 64/96Kbps MP3 quality. I honestly think that there are FM radio station on my Audi Bose system that sound better than Sirius running through my Audi OR my home stereo. It really is dissapointing.
If you can't tell the differece between 96Kbps MP3 and 128Kbps MP3 it may suit you. I give it a 3 out of 5 stars with the complaing being sound quality.