I'm in the same boat. Replacing a 20+ year velodyne uld12.
My listening space is in our family room which is 4200^. It's adjacent to our kitchen/dining which adds another 2990^. The final kicker is we have a arched hallway leading to the front of the house which adds at least another 3000^. Even more if the kids bedroom doors are open.
So you're looking at 10000^ in a best case scenario. Obviously a 12" sealed sub is way over its head.
Now having said that. I've been happy with my current setup. I will admit I've never attempted to listen at reference levels.
Before buying our current home, I lived in a much smaller home. I had the same setup and the same sub in a space about 1700^. It had more 'pressure' but I haven't been dissatisfied since the move. We been in our current home for over 15years and I've never felt the need to upgrade.
Now that I'm forced to get something I decided on the Psa s1500. It's on the way and will be here Wednesday.
At some point I may add another sub but there are only a few locations I can place it due to size limitations and the open design of our home. You can find enjoyment even in less than desireable circumstances.