Best subwoofer under 2K?

I've been very happy with Rythmik. They sound as good as my REL, they are adjustable for a number of things needed for room acoustics, and they do not have the markup of REL. A better value, in my opinion. Here are a couple of links which go into a bit more detail. Good luck!

https://www.rythmikaudio.com/reviews.html

Hsu

Also, check out data-bass.com

First, you want a pair of subs not just one.  You’d be hard pressed to do better than two SVS SB2000 Pros for $1700.

https://www.svsound.com/products/sb-2000-pro

I have an SVS PB2000 Pro that cost less than 1K and use with my JBL L100 Classic speakers.  I am quite fussy but love the sub.  It is perfect for my needs.  Don’t make the mistake I did and get the sealed box, not ported like did.  I had to use the foam port plugs for best results. 

My choice: 

Very happy with my pair of JL Audio. $1400/ea. Got on sale for $999/ea.