There are loads of website that give unbiased customer reviews of car stereo equipment.
It is buying a car, you would be better satisfied shopping where you can try out stereos in a display, write down the make and model and then go home and do research on the internet and see if people generally liked or disliked the stereo.
I like the C-Net web site. You said you were interested in CD player, you may not have one now but ask about ipod compatibility with what ever stereo you buy. I drive a lot and rarely listen to CD's anymore, everything is on my iPod!