If you are thinking to move on DSP, maybe dsPIC microcontrollers can be a good start as they have DSP engine built in that allows fast multiply and divide operations with arrays. For instance dsPIC30F2012 is a 16bit 30 MIPS MCU with 24kB flash and 2kB of RAM, 8channel 12bit ADC and other common peripherals. With these parameters you can start simple DSP applications before you move to better and more powerful.

This test board is really simple to build - simple LM7805 voltage regulator in power supply side, and MAX232 for RS232 interface. Other I/O pins are left open for prototyping. Seems to be that dsPIC’s aren’t very popular among hobbyists as there aren’t many projects published in the internet. But thanks to built in DSP engine things can change.