I just scored a DIGILENT ARTY S7 FPGA board, which is the perfect platform for the RRB project. It has a Spartan7 XC7S50 FPGA and best of all, 256MB DDR3 SDRAM on board already. So I don't have to run a SDRAM interface over PMOD connectors, which was risky from the beginning. And it has Arduino compatible (3.3V) headers. Now I can design a shield with all my crazy audio hardware. All block diagrams will be updated in the near future. Good times.

This is the new system concept.