Hi David,
I'm running the MidiSport 2x2 and 4x4, both without any problems after installing the midisport-firmware package on Debian. In earlier times I ran the 2x2 without that package, which is equally simple: you just need that firmware loader that I forgot the name of, the firmware files (downloadable) and a udev rule to upload firmware on connect.
I'm currently not at home to look that stuff up, but could provide you with those things if necessary.
I don't have any experience with the Motu devices, sadly.
HTH,
Thomas