[Wayne A. Pflughaupt]

I would call a room symmetrical if the walls are parallel to each other, and the ceiling parallel to the floor. E.g. "shoebox" dimensions, or something along the lines of a bedroom as opposed to a family room with a cathedral ceiling that's fully open to upstairs, kitchen, entryway, etc. Make sense? Every room has to have a door - that doesn't make it non symmetrical, in and of itself.

That's not the same thing as not being able to place your speakers symmetrically in the room for some reason. If someone's subs are the same distance from the walls behind and to the side, then their placement is symmetrical. I can't tell for sure if yours are placed symmetrically or not, since you referred to "the subwoofer" in one sentence and "each sub" in another. Regardless, it's best to take measurements of them both together and separately.

Regarding the BDF, it has both XLR and 1/4" plugs input, can I switch to XLR if I want to use my preamp for 2ch audio and switch to 1/4" plugs input if I want to use my receive for HT ?

As long as you don't mind manually swapping out the cables. There is no "switch" between the XLR and 1/4" inputs. They are most likely internally connected, and as such there would be no isolation between the two systems if both were connected to inputs at the same time.

Regards,
Wayne