I am pretty sure XM is digital and it certainly sounds better than FM in my TSX but it does not sound as good as even 128kps MP3's and certainly not CD quality. So what is it supposed to be equivalent to?
xm is not quite as good as a well recorded cd, sacd or xrcd. It is much better than any mp3 because there is no compression involved in the storage or transmission (Sirius slightly compresses the music to make th soft music sound a little closer in volume to the loud passages). You can notice diiferences (slight) in front to rear layering (XM is more 2D as opposed to 3D); there seems to be slight increase at 40hz and a droppoff below that; there is less "air" than the best recordings out there. That is, if your system is up to showing these facets of the music. No stock system is capable of doing this. XM is definitely worthwhile in th eyes (and ears) of this picky audiophile. Hope this helps, JPS
p.s. 128k really sucks the life out of recordings, go up to 256 at least
You can't really do a comparison to mp3 bit rates because it's not compressed. It's more like hearing things at a concert hall(CD), in an arena with horrible acoustics (XM), at an open air field festival and you're all the way in the back (FM) and at some backyard rock show with just the small guitar amps (AM).