this is not a great answer, but as with many products with multiple outputs (like 8 channel audio mixers), you can sent 6 of the outputs (for 5.1) to a monitoring system, so you can control all 6 channels. If this is a low end analog monitoring system, you will need to get AES-Analog converters. Or a digital mixer (like a small Yamaha or Behringer). Not ideal. AJA, Blackmagic, AVID, Matrox and MOTU editing interfaces are not ideally setup for 5.1 and 7.1 surround monitoring, but it can be done. If you had a single ProTools 192HD interface, you would be doing something similar, by just having 8 discreet outputs - and you are on your own for monitoring.