Sub suggestions please

I have a pair of Volti Razz horn speakers. The bass is pretty good in my room, but bottom out around 35-38 hz. Also, the bass is just a little - imprecise? I'm sure it is a room issue, not a Volti issue.

I decided to try a sub, to go just a bit lower, and to focus the pitch a little. My first try worked great - a KEF KC92. It is small, but very mighty. Two woofers, both facing outwards, each with its own 500 wpc amp. It has clever DSP settings that really worked in my room. And the blend is better than I hoped. I love its size, it wonderful tone, and the fact that it is easy to blend with the room and with the main speakers. 

I'd take a listen, if you can...

See if you can swing two SVS SB-2000 Pro.  The app makes adjusting them easier and having two should reduces node and dips.

Horizontally opposed dual 15 inch  Rhythmik G25HP. 

I have a pair of Rhytmik F12s that made a huge difference in the music reproduction with my Fyne F-702s, which have only 8” woofers.  Not available in walnut, but the walnut vinyl wrap suggestion from gkelly has me thinking.  Price was right at under $2500 for the pair.

Have been searching for new sub with walnut aesthetic myself.  Another possibility is Vandersteen.  Only issue is that their walnut, to my eyes, looks a little more like cherry - reddish tint in the finish.  But really nice subs.