I also recently picked up an Intergra DHC80.3 which has Audyssey XT32 and SubEQ, and I also purchased a rack style 2 x 2400 watt x 4ohm amp from Funk Audio to replace my noisy QSC RMX-5050 (even modded the fan noise drove me insane). The amp uses Alldsp.com software for EQ, and is somewhat similar to MiniDSP software in functionality.
I setup my 2 AV15H subs on the Sub 1 and Sub 2 preouts on the 80.3, and calibrated them both in "2 CH" (i.e., had Audyssey calibrate each signal independently). I came up with this after playing around with the distance controls and crossing my Paradigm S2 bookshelves at 120Hz..
I've been trying to incorporate the SB13-Ultra (which is placed nearfield at the back of the room, vs the 2 AV15H subs which are located at the front flanking the Plasma and acting as "stands" for the S2's). Basically I'm using one of the RCA preouts for Sub 2 on the 80.3 (which already has Audyssey applied to it) and trying to see if I can use the DSP controls on the SVS sub (LPF, phase, room compensation, etc) to keep the FR as flat as possible.
But so far no luck. Any hints as to how I can incorporate this puppy in the best way possible to gain some headroom while improving or at worst not hurting the FR?
Given the response I'm getting, is this just a fruitless exercise? Figured I'd add it in to gain as much headroom as possible. Even though I don't really need it in a ~1800 cubic foot family room.