Subwoofer Advice

For your budget, it would be hard to beat a pair of Rythmik L12s.

Those are what I currently use with my Borresen X3 floorstanders. The Borresens have the tightest, cleanest, most dynamic bass of any speaker I’ve owned among dozens, including panels, yet the Rythmiks still keep up pretty well. I don’t doubt there are better subs out there, but I doubt any of those can be had for under your budget.

The L12s have a braced cabinet that weighs in at 50lbs, a cast aluminum chassis driver, a linear power supply with massive transformer for the amp, and a solid aluminum backplate. Those are quality features you won’t find with similarly priced products from the likes of SVS. 
 

@helomech I checked out the Rythmik L12s and they look like great bank for the buck, but it seems, from what I'm hearing hear, is that I need balance forced subs which are double my budget. So, I guess I'll be doing without whilst saving up for these. Thank you for the suggestion though!

Dynaudio make great subwoofers

their 18s duall 9.5 in model  is inexpensive 

@oliver_reid Thanks Oliver, they look good, but they are a tad big and $2400 ea (plus EGF @ BB)

I checked out the Rythmik L12s and they look like great bank for the buck, but it seems, from what I’m hearing hear, is that I need balance forced subs which are double my budget. So, I guess I’ll be doing without whilst saving up for these. Thank you for the suggestion though!

I don’t have much experience with balanced/opposing woofer subs, but I have heard a number of full range speakers that employ the same principle (KEF for example). I can’t say I was particularly impressed with their bass, but that might have been due to a multitude of other factors. To my ears, the opposing woofer designs help to mitigate audible cabinet resonances, but don’t make the bass sound any tighter. At least that was the case with those full range speakers and the small KEF subs I’ve experienced. 

If you’re set on that design type, I would heavily consider the Elac Varro Dual Reference subs. They seem better built than the comparable KEF offerings. With a typical dealer discount they can probably be bought for $2K/each.

I was considering upgrading to the similarly priced REL S/510SX subs. But the Elac is an attractive proposition because it allows real-time adjustment with the built in app. That would make integration much easier I think.