I didn't care for the sound from the stock radio at all. I had a new unit installed, it sounds a hundred times better and I can hook up my XM. I haven't tried the amp adjustments to see what affect that has, will try that soon.
I will tell you be very careful if you replace the radio, hire a good installation company or person. I was going to do it myself but the unit I bought was very complicated and I could not find a whole lot of resources for the car. No direct installation kits, pretty much a custom job. For some reason the wireless entry isn't working since the new radio went in. I started a discussion on the site, if you are considering replacing the radio and care to follow the problem I had.