Looking to get a cd changer for a 2001 G20 with the stock system. Any advice on this? Not looking for anything special, just something that sounds decent.

Unfortuneatly, there are very few changers that will be compatible with your stock system. FOr the price of the stock changer, you could get a nice kenwood head unit and changer, or a pioneer head/changer combo... Or for a cheap way out of it, just RF modulate it.

if you add on an fm modulated changer it won't sound as good as an aftermarket cd headunit . Because an fm modulator plays through your radio and is basically a static free fm signal

Yeah...I'm still considering an FM modulated unit, but not sure I want to go that way.

Any specific recommendations on head units/changers?

I have an older G, and when I found out that a changer compatible with my stock system would cost $350 off eBay, and $600 or something at the dealer, I got an mp3 headunit instead. I was going to add a changer on to it, but I don't even need to because I can fit much, much more music on 1 mp3 cd, which accesses faster than a changer and with little or no noticeable difference in sound quality. I got the Kenwood MPV 7019...http://www.crutchfield.com/S-JX5oFiDFkHh/cgi-bin/ProdView.asp?i=113MPV7019&s=0