Just an update on this thread. I ended up swapping out the Klipsch 12" for a Mission MS-200. The reason for this was that due to a space constraint. The big Klipsch R--120sw had to go to go beside the sofa instead of under the TV between the mains, and was VERY localizable (if that is even a word). The MS-200 fit neatly into the only space I had for it in-between my main speakers and under the TV, and what a difference. I am using LFE+Main mode for stereo music and it is blending nicely. I have a fuller low end to music now with the mains set to large and the crossover for stereo set to 60hz. The LFE for TV/movies is great. It can hit the volumes I need without crapping out, so I am happy.
Yes, the MS-200 could be a little fuller under 35hz, but it was on sale, and the next option that would fit in the space (front firing, sealed, dimension wise) was an SVS SB-1000 at almost triple the price of the MS-200.
I am impressed with the MS-200 in a value or $$$ way. No real reviews or tests on it that I could see online. I have the equipment to run REW and may put it through it's paces and post here if I get a chance.
Now that it is wired up for it. I may try out a second sub next to the sofa one day, if I find a bargain.
Amateur tip (that I am sure many others have thought of before me!) Used a tone generator to find and remove a bunch of resonant vibrations in and around the cabinet under the TV.
On another note. I think it is sad that Denon, Marantz, et al, don't make lower channel count receivers at higher wattage. For example, they should make a line of 7.1 receivers in low and in higher power, do the same for 9.1, etc.
Just a thought. If you only need a 5.1 setup, they don't make a receiver with balls, but they easily could.