Rpi 2 will run on 2 amps or so. rpi3 needs 3 amps. I know a few guys have used the kali and piano on a rpi2 using moode or volumio. So its maybe your best bet Mike. An rpi2b is good n cheap. Might need a new box made up but you could use the sparky panels initially. The other board is to multiply the voltage from the 5v supply to the 19v for the amp board by way. Glad youve got it to work