Although, you have already gotten a fair bit of advice on this thread, it may be worth exploring your options a little bit more. If you are looking to upgrade to another SVS sub, from your single PB2000, I would recommend a PB3000 over a 2000 Pro, and I would probably recommend a PB4000 (or a PC4000), over a PB3000. As you move-up the SVS food chain, you gain some things that you may want. Here are some things to consider, as you also consider what you are able to afford, or are willing to spend.
Your room size is about 2300^3. That's not a really large room, so you will be getting some room gain that will help to augment the frequencies under about 25Hz. That's a plus! You don't mention whether or not you are on concrete or on a suspended wood floor. If you are on a suspended wood floor, that will be another plus with respect to very low-frequencies.
A suspended wood floor will resonate sympathetically with very low-frequencies, creating low-bass tactile sensations which correspond to the special effects in movies. Concrete will not resonate that way, and consequently, most people need more <20Hz SPL when they are on concrete floors. (Carpet or wood flooring, on top of concrete, doesn't increase low-frequency resonance.)
Bringing this back to the subwoofer options, moving-up to a PB3000 will offer you a lot more SPL at every frequency, compared to a PB2000, where a Pro would be a much more modest increase. And, the sound quality should be a bit better as well. The PB3000 may be SVS's best value for the money. I think you would notice that upgrade much more than you would if you went to the 2000 Pro.
But, and this can be an important but
for some people, the PB3000 is still not a low-tuned subwoofer. Quantifying the difference between a subwoofer which is tuned to about 19Hz, and one that is tuned to about 15 or 16Hz can be a little difficult. You can look at outdoor measurements for the two different subwoofers and see what the max SPL numbers are below 20Hz. But, if you haven't actually heard a lower-tuned sub, those numbers may not be very meaningful to you. Here are some test results that you can compare:
You will notice that the PB3000 holds its own very well with the PB4000 down to 20Hz. But, at 16Hz, there is a difference in max output of about 11dB between the PB3000, and the PB4000 in Extended mode. To put that into context, a single PB4000 would produce approximately as much SPL, into the middle teens, as four PB3000's could produce. (The disparity would be just slightly greater with PB2000's. The PB3000 doesn't really go much lower than the PB2000 does.)
The way I arrive at that comparison is as follows. A doubling of subwoofers nets an increase of +6dB. Doubling that
pair of subwoofers nets another +6dB. So, four PB3000's would produce 12dB more max volume, at 16Hz, than a single PB3000 would. An 11 or 12dB difference at those low-bass frequencies is enormous!
The first question I think you need to ask yourself is what are you really looking for? Are you looking for more of what you have now, combined with slightly better sound quality and more features, or are you specifically looking for more <20Hz performance? The reason that subwoofers become larger and more expensive, as they play lower-frequencies at higher volume levels, is because those lower-frequencies are harder to reproduce. They require larger cabinet volumes, lower port tunes, (perhaps stronger drivers with more amplifier power), and more DSP directing the amp power into the lowest frequencies.
If you are on a suspended wood floor, in a room that size, you may already be getting pretty satisfactory low-frequency SPL and TR (tactile response) from a subwoofer which is tuned to about 19Hz. But, if you are on a concrete floor, or if you feel that you want to explore lower-frequencies, then you will need a lower-tuned ported subwoofer in order to do it.
That's why I used the example of it requiring about four PB3000's (or PB2000's) to equal a single PB4000 at 16Hz. You can't just add multiple ported subs and expect to get significantly more low-frequency SPL. Each individual sub will still roll-off wherever it is designed to roll-off.
In an early post @Basshead
recommended that you jump all the way to a PB4000, but he didn't really explain why it might be worth your while to do that. And, neither did the subsequent posts. Unfortunately, no one else can put himself in your exact position concerning what you are really looking for with an upgrade, or with respect to subwoofer costs.
But, I thought it might be helpful for you to understand some of the advantages involved, as you move-up the SVS ported subwoofer food chain. Good luck with whatever you decide!