i would also reccomend looking into devboards from the major manufacturers. TI has some stuff, Analog has its sigmaDSP line which is pretty interesting. it has a nice GUI for doing filters and such easily. Freescale also inst bad. if you want something quick, you might try looking into the old tonecore pedals from line6. they have stereo in and out, and an onboard dsp and microcontroller. otherwise you will have to roll your own.