I have a Qu Pac and normally run the mains with the AES out into the DBX360 input, works great, sounds clean. When I run the system with aux subs I still use the AES to run the mains and an analog out for subs.
In the DSP I add delay to the AES input to compensate for the additional latency on the analog sub aux input, I can't remember what that delay is right now!
If I'm doing bluegrass/acoustic acts with a larger system I always go with aux subs.
The QU's only have one AES output but it assignable to any of the QU output sources.