we’ve just opted for a RME Madiface USB + Antelope Orion32 for a studio here at the University of York Music Research Centre, to go with the new Mac Pro. In initial tests it seems to be a great combination. An additional Orion32 could add another 32 analogue I/O. Previously we have used MOTU PCIE424 + 24IO setups for installations with the old Mac Pros, which was a good combination, but MADI seems to be the way to go at the moment. Not sure if MOTU are going to continue their "audiowire" products, since they don’t work with thunderbolt. The Orion32 has a USB interface, but it didn’t work with bootcamp on the new Mac Pro, which was a requirement for us. Also the RME software/drivers seem superior.
yes, we thought about going for RedNet which looks very nice, but that would be a significantly more expensive and less compact option, since for a studio we’d require a PCIE card, a Thunderbolt to PCIE breakout box and 2 * RedNet2 DA boxes (for 32 IO).