Flexinoodle and I recently finished our collab: the fnpSID. It's a stereo mbSID v2 with added gm5 support for easy PC<->SID connection.
The pcb is basically comprised of a core module, a gm5 module and two sid modules and 5 banksticks.
It runs off a single 9V-12V AC/DC wallwart.
Since the gm5 gives us 5 IO ports, you can hook upto 4 other MIDI devices up to it.
It has the option of linking together multiple of the fnpSID PCBs to allow for either multiple stereo synths each