Recommendations for a new subwoofer?

Yeah unfortunately, almost no one does bass definition better than REL other than DIY open-baffle.

Their carbon subs are even higher speed and definition.

Here’s the update I promised in my previous post: after living for a few weeks with my new ELAC Varro ES500 which I think has probably had enough time to find its voice, I’m liking it quite a lot. My first impressions were, as I said, that it was startlingly different from my old REL S/2, and this is still true, but what I’m hearing is added warmth, though not muddy at all. It seems to blend a bit more easily with the rest of the sound spectrum. The REL held bass frequencies in an iron grip, which certainly has its appeal (I lived with it for 10 years, after all, so...), but so far, I’m liking the ELAC better. 

My musical tastes are a bit all-over-the-place, though predominantly classical, as I am a (mostly retired now) professional musician. But I still revisit my misspent youth a lot, which includes the popular music I grew up with (think San Francisco in the late 60s) across the genres of rock, prog-rock, and English folk. I’m also a great admirer of Broadway shows. The latter, when well recorded, are particularly good for showing off the attributes of a system, and here I’m finding the ELAC sub to be a very entertaining and appealing addition. 

At the beginning, the sub was connected via line-level cabling, but I couldn’t resist the temptation to try out the speaker-level option, so ordered some cables from Blue Jeans Cable just to experiment with, and lived with that configuration for a week or so. A few days ago I changed back to the line-level connection, and by a very thin margin (which might simply be my imagination at work) prefer things this way--just a tiny bit fuller and more musical. 

Hope some of you find my experience of interest. And again, your input here was greatly appreciated.