I have had luck connecting 2 XS units to my Qcon Pro X but once I bring in the third XS all hell breaks loose. Cubase freezes after about a minute of playing any project (new, old, small, large). We have been working very closely with tech support on this, and they first suggested it was a problem with the PC. So we took the Pro X and the three Pro XS’s into my set up - and I couldn’t even get as far as loading Cubase.
Getting all 3 expanders to even be assigned with the right Mackie Control i/o was a nightmare in itself. Multiple reboots and restarts of Cubase were necessary and at one point Cubase said I had an invalid e-licenser account.
So the bottom line seems to be, that it works with 2 expanders but not 3. Tech support at Icon/mixware are evasive about whether anyone using Cubase has tried 3. They have been helpful and good to work with, and I am currently awaiting their reaction to the news that it’s not some anomaly with my husband’s PC, because it fails on mine to a much worse degree. I cannot open Cubase with all 3 expanders. Just thought I’d look around to see what other experiences have been.