My experience with subs is... not using subs.

I don't know what your mains are.
You said in the
other thread that you have:
Rotel RC1070 (pre-amp)
Audio Research S10HO (sub)
A friend of mine uses the sub for HT only not for stereo.
Usually (how it started) the sub was to substitute the two main speakers when they were to small (no woofers) and to play earthquake type info in cinemas.
I don't see any interest in using subs if the two main speakers are good (quality and LF extension). This has to do with a few aspects related with the quality of the equipment in general, speaker drivers, quality/amps type, dual/stereo for mains, position in room and nulls/disturbances. Is just my general opinion, that I can change at will or for different cases/necessities.
AR (Acoustic Research) S10HO
It is equipped with an input terminal of the two types of low-level and high level.
It is equipped with auto-sensing capability and variable adjustment of the crossover frequency and input level.
Crossover frequency 50Hz ~ 200Hz (continuously variable)