I would call my Cisco account rep and ask him if I could demo some phones and possibly give you one of several phones to try out on your network. If you are considering a large purchase of new phones, I'm sure he would be willing to loan you a few different models to help with the decision making.
Sorry I'm not providing a recommendation, maybe someone else will chime in with a recommendation.
Hope this helps...
Please check the below document for details on our wide range of IP phones and their key features.
Let's put it this way, if you are buying a car, you already have a list of what you wish for it to have, and a budget, correct??
Same principle applies here. What do you need the phone to do??? How much do you want to spend???
As already suggested, you should reach a Partner / Cisco rep so they can assist, or pre-sales team if you're a partner.
If you want something nicer, the DX series are pretty nice.
beyond what everyone already said ... take a look on this link: Endpoints Comparison.
It's a quick comparison for the major features.
Hope this helps.