I’m using a Universal Audio Apollo Twin with a Motu 828 connected by ADAT to increase the number of inputs, and it’s been pretty wonderful so far.
I have to make sure that the clocking is configured correctly, since the Apollo only has ADAT in (no ADAT Out), so the Motu has to be in charge of the clocking, but other than that, it doesn’t do much crazy stuff. I only have 10 simultaneous ins, though, so I’m not typically rendering that many output channels at a time.
From a CPU load perspective, it doesn’t seem like whether you use ADAT or not matters that much, since the Saffire will probably be dealing with the clocking/syncing to the OctoPre