What do you want on it? What source are you going to use to play your music? Does sound quality matter, or just how many features its got?
If you're not bothered about being able to play CD's any more (either cos you've got all your music on your iPod or on USB sticks), then check out the Alpine IDA range. I've got an IDA-X100 in my car, it's the model from a couple of years ago but it's absolutely bloody brilliant. The replacement model for it is called the IDA-X305 I believe. Anyway, I just connect my iPhone or a USB stick up to it, and I've got tonnes of music on there, with a user interface very similar to use as that of an iPod Classic. You get a big knob in the middle, and a central button, and you browse by turning the knob either way, then hitting the button to select something. Just like on an iPod!
The only time I've missed not having a CD player at all since buying it is when I've bought a new CD from a shop, and want to play it ASAP. I have to wait til I get home and have ripped it to iTunes then synced my iPhone now. But that's the only minor inconvenience.
Oh, and Alpine are about the best make out there, you get good understated quality products from them, no flashing neon lights and widgets you don't need, just simple function and good performance. If you do want a CD player mechanism too still, then check out one of the other Alpines in the range as they still do plenty with CD players too, and many of them have still got the ability to connect to an iPod or USB also, you just don't get the excellent user interface that you do on the IDA series…
That helped at all?