Trying to decide on a new sub purchase is more difficult than it should be. The problem I'm having is that I'm trying to decide what would be best for me while reading subjective advice from so many different forums. I'm trying to stay under 2K and get the best bang for the buck. I will most likely have this sub for a very long time. I'm not an "upgrade all the time" type of person. I honestly think I would be happy with with just about any quality sub in my price range but I will take one last approach and ask directly. Room size approx 4000 cubic feet. Current speakers are Definitive Tech BP2002 and their matching center and surrounds. HT use vs music 60/40. Build quality and appearance are high priority. Huge boxes are not ideal. I'm not looking for the highest SPL but I am looking for significant output below 30hz. I prefer quick accurate bass not boomy. I have been reading no less than a couple months and so far my short list is. Thank you for any advice.
Epik Empire (could be dual)
Def Tech Supercube Trinity (I can get around 2k)
Def Tech Supercube Reference
I'd recommend a pair of Rythmik FV15HPs if you can swing it. You'd get good 20 hz output and articulation with them. Since you mention you're not looking for high SPLs even a single do about as well for you as the PB13 for less money.
My second choice would be the Empires. They're also musical but you're giving up some sub 30 hz output relative to the Rythmik.
If you are looking for one and done, you may want to check out a submersive. Just keep in mind that you have a pretty large room and depending on your taste for bass, you may find that 2K worth of sub will not fill it to your liking. A submersive would be about as good of a start as you could get though.