Place the 2WQ where you chose...
if its on the left side of room its now the left channel
if its on the right side of room its now the right channel.
Walk over to your existing sub that has a right and left speaker level wire feeding it.
Leave just one connected while removing the other ch speaker level feed wire connecting it to the other sub.
Make sure both subs are in same phase red/black same as main speakers.
Confirm the left ch amp feed is going to the left sub.
Confirm the Right ch amp feed is going to the right sub.
Spike both subs, bubble level, and snug tighten all lock nuts. Don't forget this part as its important as is the laser tilt back and leveling for your main speakers.
Now re adjust settings to preference and let us know what you experience.
JohnnyR