The requirements you mention are very general, in order to recommend something it will be useful to know a bit more of your design, it should not be a complete design just some sketch in which you can define if you are going to use ADCs, analog comparators, any serial interface, etc...
If you want to start your development from something easy to handle I suggest you to consider to use our development platforms like Tower System Modular Development Platform specifically the TWR-K20D50M: Kinetis K20 50 MHz Tower System Module or also you can find something interesting on Freescale Freedom Development Platform which are even simpler development platforms.
