All of these cameras have merit.
All comes down to choice and the needs you have from a camera. I'm very happy with my CP4500 and most others are happy with their CP9XX
The CP4500 being the top of the range in the swivel head series. The highest you can go using the sharper FC-E8 Fisheye lens is the CP5000 (But you lose the swivel head) Again people who use this model are more than happy.
If you plan to display in a viewer applet less then 500 x 400 any camera with 3mp or more will do the job nicely! Obviously the more pixels you have to start with will always help with your final result.
My personal opinion is that the CP5700 & CP8700 although awesome cameras in their own right! Are very large when connected to the FC-E9 plus adaptor tube then FC-E9 Fisheye lens is definitely softer on the outer edges.
Good luck with your choice (really you can't go wrong) all these Nikon's are great cameras! I look forward to seeing some of your results, if you need pointers - I'm more then happy to help where I can.