In my limited experience with the Clarion Diversity, I guess overall I've been quite fortunate.
In that, the wiring is still mostly there, I know the speakers, sub, tape and cd changer work.
The gutting thing is the head unit........
Someone had literally ripped it out, so the facia panel connector isn't quite right, so causes a high pitched whine, or when pressed hard, a fully working system !
Sadly, this didnt last, so tomorrow I'm going to ring the service centre and have a chat !
With regard to other units, yes there are units that will do all sorts, but I have to disagree slghtly with gavbriggs, as if you get stopped for using the stereo controls (not on the steering wheel), you may get some points and a fine !
However, some of the newer Clarion units have input for steering/stalk controls, and look quite nice, so you may be lucky !