I recently picked up a Zoom R16 multitrack, and that’s working really well for me because it functions as both a standalone 16-track (8-in) recorder and an 8-in PC audio interface. With my A4 and Octatrack I like to stay away from the PC, and the Zoom lets me do that, but I can deploy it as a soundcard if I want to combine my hardware with Live, for example.

If you can wait for Overbridge, you should be able to route your MD into your A4 and then record your A4 directly via USB as separate tracks. Of course that’ll require the PC, but you could just use it as a straight recorder rather than syncing it up etc.