I'm using 4 of these:
2 of them with about 16 120mm fans on one channel.
2 of them with 8 140mm and 1-2 120mm fans each on a separate channel.
The AQ6 has no problem with that, although I got no RPM signal.
When I tried to connect the ones with the 140mm fans to the same channel I got the over current warning and the fans wouldn't spin.
Bottom line, shouln't be a problem running 3-4 fans per channel as far as I can tell.
My AQ is watercooled so the fan controllers are ~ 30c even when running the fans at much lower voltage.