How does adding a second subwoofer improve your systems SQ?

sound quality

Avanti,
Having two subs is a great advantage to achieving a balanced sound if you have limited room to position them.    

This is what I was waiting for. Unless you have a dedicated audio room, I don't, there are definite limitations to most all rooms. My system is in my living room. I simply can't put subwoofers where they might sound best. I'm confined to placing my sub next to one of my main speakers. Avanti, so your thesis is, buy a second sub and place next to the other speaker and enjoy the music. 

Thanks ggc. I just ordered my second sub. Actually, thanks too all
that contributed to this discussion. It was informative and at times entertaining.