My experience adding subwoofers to 2 channel

My Kappa 9 speakers are rated to 29hz and they sound pretty good in my 18x24 room...powered by McIntosh mc1.25 amps...l was looking for another layer of bass to enhance the first experiment l took my SVS pb16 ultras from my theater room and tried them sounded terrible,didn't blend well..couldn't hear a difference until you turned in up then it rattled the room final experiment worked..l used 4 Velodyne minivee subwoofers(1000 watt rms class D sealed 8 in.) and after hours of calibration l hit it......lve got the bass response that exeeded my expectations. ....l should have done this along time ago....can anybody tell me of another subwoofer that may work even better?
Hello vinnydabully,

     What you apparently discovered by accident is called a 4-sub distributed bass array system.  The key is having 4 subs and I've been using one for the last 4 yrs with large Magnepan panels.  The Audio Kinesis Swarm and Debra are complete 4-sub DBA systems that sell for about $2,800, and the 4-sub DBA concept works like a charm.  Here's an Absolute Sound review of the Swarm:

    As you've discovered, you can create your own custom DBA using whatever 4 subs you prefer.  The concept is based on scientific research done by Dr. Earl Geddes and Dr. Floyd Toole. 

    I and others have started threads on how well this concept works:

     You can google 'distributed bass array', 'geddes' or 'toole' if you'd like to read more.

4 JL Audio Fathom V2.  That should scare your neighbors to death.
After reading the threads here and doing further research,I added a second sub last week.I was so pleased with the improvement I've got two more  on the way to complete my 'swarm '.
My subs are located behind my main speakers in the front corners...behind some silk cant see them ...makes it very "steathy"and cool......l will try all four corners McIntosh C52 pre amp has switchable outputs for tri-amping so l can turn the subs on in groups of two or turn them off from the preamp front panel...very convenient. ....the "swarm configuration " will be the next phase ......the receptacles and audio cables are going to take some planning. ...thanks guys for the cool advise! 
Its amazing when it comes to bass how much better more is than few. With subs unlike the L/R stereo pair the subs can be completely different and located almost at random and yet still work just fine. So they can be "cobbled together" buying whatever you can whenever you can add and still wind up with excellent results. This might even be the best way to go, because of all the flexibility being able to adjust crossover and level of each individual sub. If you can afford a better sub great, but if you can only afford a cheaper one that's great too because more is always better.