Best subwoofer's for $2k/pair???

Please take a look at the Paradigm Defiance Series Subs. Start at $400 and go to $1499. Starting at $549 they have Anthem Room Correction which can be run on an Apple or Windows PC or a Mobile Device, Full App Control of the sub from a mobile device; which allows you to find all the rattles in your room at specific frequencies by doing a "Sweep" (from 20Hz - 120Hz that you can lock and adjust in 1Hz increments) so you can isolate those things rattling at every frequency and know what frequency it is. It also allows you to hear where the dips are in the room at those frequencies. And finally, all those have wireless capability as well if you can't get a physical wire run where you need the sub to be.

X-Series made in Canada from $999 - $1499 and V-Series made in China from $399-$649. X-Series woofers have two US Patents = 1) Increases output by +3dB, so double the output, and 2) Reduces the distortion by 50%, so cuts that in half...Musical and Dynamic for movies!

https://www.paradigm.com/en/overview/series/defiance-series

A pair of Vandy 2wq's should be under $2K.
And, unlike most other brands, they are built like tanks.
You need to buy the external crossovers, which, once you settle on the proper impedance, are around $200 for fixed values.
The best part of the Vandy system is that your amp is relieved from the power draining bass frequencies and can perform at higher efficiency.
Bob

I'd look for a couple of used SVS SB13 Ultra subs.  They should be available for under your budget.  I think you'd have a hard time getting more bang for your buck.  If you prefer new, increase your budget and look at the SB 4000.  Another option is a pair of Rythmik F12s, also in your budget.

I have an older ’R-series’ REL (R328, $1600 in 2013) which at the time was their top-tier (now it’s the S "Serie"). Yes it’s good - but not $1600 good.

With that in mind I briefly considered REL S-series when shopping dual subs for my main room. Then I moved on - all things considered I think they’re overpriced. I looked at Rythmik, Hsu, PSA and finally ended up taking a chance on dual Syzygy SLF870’s, with some bank to spare ($$$). I haven’t looked back.

ps: consider moving your post to the Speakers forum ... it's a bit off-subject here in Music.

REL, great. Their $1000 T/7i is a winner, the T/9i is a bit more but delivers a lot more. They are the pros out of this group you mention.

SVS is home theatre stuff but some users think they’re ok for audio too.