I overshot by buying two subs. My HT is 2-3 months from completion, but buying the equip. b4 its ready(so I'm ready).
Took them to a friends house with a dedicated HT (13x17'), cranked those suckers up-mother of god- shook loose a filling in my back molar!. My HT is the same in dimensions, so I guess one is going out to the Family room system(Elan in-ceiling surround).

In terms of raw acoustical power, perhaps two strong subs may be overkill in your situation. But with a setup such that the two subs blend well with the rest of the system, some of us find a benefit to having two subs. I have a preference for running my subs in a stereo configuration using an Outlaw ICBM. Whether two subs are run in stereo or duplicate mono, many people find that, with good placement, the interaction of two sets of standing waves at various frequencies allows some rooms to have fewer strong node or null spots in the prime listening area as well as throughout the room. Since you already have two subs, unless you really want to return one within the 30 day trial period, perhaps take the time to experiment with a single and a dual sub setup.

MurphyMan:

Do you mean even the volume control won’t help?

Wasn't really a "volume" consideration- just TOO much sub!
Granted, my HT will be acoustically better- I'm soundproofing the walls with micro board, but I suspect the second sub may be overkill. I will definitely have my CEDIA installer guy check out all placement possibilities, but who knows?
I have a family room with 5.1 surround also- so the second sub has a "home" if it doesn't work out.

Go the stereo sub route. This will increase the realism of stereo and mulit-channel music presentation. The added sub will increase low frequency extension by a few Hz by way of mutual coupling between the subs. The convention of a single mono subwoofer came from the motion picutre industry for movie playback - it was never created with music reproduction in mind. A mono subwoofer is an unacceptable compromise for music because all acoustic mixing in the room of the low frequencies in a recording is destroyed.

I have three subs in a room smaller than 13x17 and they work fine. I used soundhounds stereo sub idea and then added another for the LFE. Adjusted the volume of each so they are not overpowering and cut all at 80Hz and below. In this setup, I have bass that is tight and clean and you do notice it move with the action of the movies. Highly recommend. You may have your subs set too high, tone them down to match the level of the rest of the system.

OK-OK , maybe I overstated, or got ahead of myself. The bottom line is I have a CEDIA installer actually involved in the whole setup WHEN I finally move into the new house/HT. So maybe it was unfair to pre-judge the 2-sub effect. I'll withhold further judgement until...