DsPIC development board recommendation
The Explorer 16 module from Microchip is a good starting point if you intend to go into power conversion. You can get a buck-boost plug-in board (PICtail) and you can dive right into developing software to control them.

PIC32 is a different animal. Its MIPS-based and doesn't have the dedicated DSP engine that the dsPIC has.

Unless other constraints block you, don't limit yourself to Microchip though. Texas Instruments has two good solutions as well - the C2000 DSP and the UCD3138 digital power controller.