what sub would be best? B&W, MARTIN LOGAN, DEFTEC

I am replacing a older polk sub,
I listen to mainly rock and country, also will use as my home theater sound as well. I want a sub I can truly count on to be there and give me that grab you by the ass bass that a good system has. I run polk RTI 7 as mains and older rm series as rears. with a klipsch reference series center all being pushed with a pioneer elite 52. My choice for subs would be:

Definitive Technology - SuperCube 4000 8" 1200-Watt Powered Subwoofer

Bowers and Wilkins - 10" 200-Watt Powered Subwoofer

MartinLogan - Dynamo 700W 10" 600-Watt Subwoofer

any feed back would be greatly appreciated.
I would look at a Rel sub It will do it all and some.
It just so happens that the April issue of Home Theater compares the $799 Def Tech Supercube 4000, the $1799 REL R328, and the $6300 JL F212. In another review they cover a system from Emotiva, which includes their $499 X-Ref 10 sub.

I was surprised by this fairly expensive REL's frequency response. It was a simple resonant spike that centered at 45 Hz and dropped off rapidly above and below that. It was down about 12 dB from that spike at 30 Hz and 100 Hz. You may get a good blend with the right speaker and good extension with boundary reinforcement, but it doesn't give you much bandwidth to work with. Home Theater worked its way around this by calling the 45 Hz frequency a +6.5 dB peak, while the -3dB point was 30 Hz and 103 Hz. But they also said that the 6.5dB peak would normally disqualify it from recommendation except that REL states that their subs are designed to rely on room reinforcement for more linear response. I say it makes it a fussier sub to position and integrate.

However, this is just one of REL's many sub models. Others may have broader response curves.

By contrast, the $1K cheaper Def Tech Supercube 400 had a flatter curve anchored by two resonant peaks at 30 Hz and 60 Hz. At the low end it was down 10 db at around 25 Hz and 100 hz. The dip between the resonant peaks at 30 and 60 Hz was a mild 2-3 dB. Using the same curve interpretation used on the REL, the Def Tech's -3dB points were 26 Hz and 94 Hz, still better than the REL. And for the difference in price you could buy two and still save money.

The JL F212 had the kind of response curve we think (or hope) we're getting but seldom do, with a nearly flat curve (-3dB at 20 and 100 Hz) from 20 to 100 Hz and a -10 dB drop at about 170 Hz.

Even the $499 Emotiva ha a flatter curve, with a -3dB point at 33 Hz, -6dB at 31 Hz, and an upper -3dB point at 117 Hz.
I've heard some Martin Logan subs and was very impressed with their ability to augment the bottom end without drawing attention to themselves. It stands to reason that a company that creates subs to blend with electrostatics is going to pay careful attention to transient response and response curves that blend with the mains. I don't think I've heard the Dynamo 700 specifically.

However, this review looks like it's a unit worthy of consideration too.

Last week I heard the B&W PV1D, which at $1800 is a lot more money, but it *is* fabulous. AFAIK I haven't heard the ASW610 (200W, 1X10"), but the reviews seem favorable.

I have a friend that has this SVS sealed box 12" sub. He mates it with Magnepans. Since it's smack dab in your price range (including free shipping) it should be worth a look. Reviews are very favorable and purchase includes a 45-day trial period and 5-year warranty.
If you get a 10" Logan, buy the earlier Dynamos used, it's what I have. They're sealed rather than ported and by all accounts more accurate than the current model. For what you'll save buying used, for the money you can get two, always better sounding than one sub. I saw one for sale the other day at a very attractive price, it may still be up.

At the opposite extreme, consider this, it's more expensive at $850 but highly regarded and it will take you all the way down to 20 Hz with good output and servo control:

Check out the RSL Speedwoofer 10!!
Another one you should look at is the paradigm Monitor 10. Goes for around $850. This small woofer goes down to 17hz. I'm actually waiting for mine to arrive.