Thanks, Mick. Two subs isn't an option right now, but one is. The question is whether adding the 8" Omega sub is going to result in a noticeable difference in this space, given that I've already got floorstanders with 6" drivers. All comments appreciated.
Is it a matter of funds or a matter of space? Most of us deal with both of these problem to varying degrees.
I think you will be happier with a stereo pair of subwoofers crossed over a bit higher than normal (100-200 hz) to flesh out the upper bass. While adding deep bass will give you more impact, you will really feel it in the mid and upper bass.
I realize that this is Louis' circle, but he doesn't currently sell a "full sized" bass module. The 8" is good, but you are trying to fill a 4,000 cubic foot volume, keeping up with efficient main speakers. My living room volume is about 3,300 cubic feet and I use stereo subs with 2 x 8" drivers in each.
An alternative that a number of users have chosen have been the Rythmik servo subwoofers. They are "fast" and if you choose paper-coned models they can blend seamlessly with the paper-coned mains. For my money, the best bargain they sell is the L12 Sealed sub at $539 shipped. It is only slightly larger than an Omega 8 and will move a lot more air.
On a related note, Louis has built custom enclosures for Rythmik components. His workmanship and quality are better than the factory Rythmik options.