I think it sounds really good, that being said I am driving factory speakers using only the head unit. I don't listen to FM radio so I can't really comment on that source. XM is fine from what I have listened to and I haven't played a CD yet. The iPod sounds great, one thing I noticed is that if a track was ripped at a low volume level it comes though on the head unit so it doesn't seem to do any level normalization. I'm going to try and play a lossless file and see if I can tell the difference.
I wish I could give you more feedback on the sound but it wouldn't be fair without an amp a