adding second set of speakers

Too funny. Especially since, if that's what it really was, it could be eliminated quickly and for free as easily as reversing polarity on one or moving one or the other out of the corner a little one way or the other. 

canibefrank - @millercarbon
well, i went and done it. i wyred up the JBL’s and pointed them in corners directly beside my listening position as my couch is at the far wall with main monitors directly in front of me. now I have set the high pass sub woofer to 80Hz so the 4 monitors are getting everything 80Hz and up. with the JBL’s up about one-third, the soundstage is pretty wide. I am liking this. Now, I did not disconnect the tweeters. Do you feel this will be an added benefit? You mention using some pillows to control the sound... please elaborate. One thing I will try is wiring the JBL’s to the full range inputs and see what that sounds like...

The only reason I recommended disconnecting the tweeters is to avoid the potential problem of you being able to localized the speakers by their high frequency output. But if it sounds good and you’re not hearing where they are then no worries.

Not sure what you mean by full range inputs. I would have thought both pairs were being run full range?

If you’re running the stereo pair through the sub crossover you will definitely want to run them full range instead. Not only will you gain a little detail by eliminating the extra circuitry, you will find the bass is better with more bass drivers.

Yeah okay I did silly stuff like this when I was a kid too. Stack em, more louder, cool. 

But I can guarantee that is all you will get more of, volume.

One trick you might try, that might actually be not just louder but better: Pick whichever pair you like best, set them up as best you can for imaging. The other pair, open up and disconnect the tweeter. Then place these down on the floor facing a wall in a corner. Since these are 2-way speakers even with the tweeter out the woofers go quite high so use a pillow or blanket to absorb as much of that as you can. You are basically, in other words, using them as subwoofers.

If you can set them up so you can't hear anything from them but low bass then you should be able to find locations that get you quite a bit more extension and improved imaging at the same time.