I agree with Randall, plus the other benefit of using the speaker outs on the s.e.x. to the speaker level inputs on the sub amp(s) means that tone and phase will be consistent with what the mains are seeing and assuming proper wiring of the whole system and placement of the subs, better integration should result.
Once you have the integration right, turn the sub amp gain way down, crank the mains up as loud as you'd want, then slowly in crease the sub amps output until you just barely hear the subs, and then maybe a hair more, and then all levels, phase and tone balances should remain very consistent regardless of music and level.
H
TH,
Jim
Jim Rebman -- recovering audiophile
Equitech balanced power; uRendu, USB processor -> Musette DAC -> 5670 tube buffer -> Finale Audio F138 FFX -> Cain and Cain Abbys near-field).
s.e.x. 2.1 under construction. Want list: Stereomour II
All ICs homemade (speaker and power next)