Best Subwoofer To Use With A Two Way Speaker System

I received my new Wilson-Benesch Vertex stand mounted loudspeakers in mid-January.  After about a 200 hour break-in period and a few position tweaks I am now in audio nirvana but without the final low octave or so.  I carefully chose my associated electronics and couldn't be more pleased.  My Sutherland N1 preamplifier has 2 outputs so I can use it to drive a crossover/subwoofer system.  
I am entirely certain that my spouse would never stand for me to add a W-B Torus Infrasonic Generator & the accompanying Torus Amplifier at about $12,000. I would like some assistance from those that have the experience to advise me of something very good to mate with my system at a much more reasonable cost.  Thanks

perazzi28, thank you for your informative response and the accompanying links, very helpful.
I would respectfully suggest the Goldenears Supersub XXL..  I love mine and have had them successfully mix with a few friends' various speakers that lacked low end. Each of them ended up buying at least one and still are very happy with them. The enclosures are reasonably sized, attractive to look at and have lots of servo processing to allow easy placement.  I find them very musical and easy to integrate. 
Thanks for the recommendation. I will take a look at everything suggested. It truly helps when knowledgeable people have valuable input.
I own the least expensive 12" sealed subwoofer made by SVS--the SB 1000 (just 1...not enough room for 2). It cost ~$500 + shipping. The sound is excellent in every way: powerful, deep, impactful, tuneful bass (sealed is obviously the way to go for music listening). This sub is quite a bargain.

The same basic sub but with more max output power (500W vs 300W) is available as the SB 2000. It's a big bigger and said to put out a lot of powerful bass. Neither the SB 1000 nor SB 2000 have room correction software. You have to adjust them by ear--old school (fine with me).

As you go up SVS' line, subs get bigger & far more powerful in the Ultra models. The 13" ultra has 1000W, DSP sound contouring, and costs ~$1,600 each. The 16" ultra, their newest model, has been getting a lot of attention in audio circles. It has app-controlled room correction software said to be very effective. Power is 1,500W and it costs ~2000 each. This unit has been compared to audiophile subs costing 2-5X as much, and it is said to be more than competitive.

If I had a big living system & needed subs, I wouldn't hesitate to get a couple SB 1000's or SB 2000's. You get great sound at bargain prices.