IMO, it should be no problem ... you could place the sub nearer to you if you feel it's insufficient.
24x16x20=7680 cubic feet (then you deduct the parts of the ceiling that are not 20; high) the room is sealed right?
or you can buy some new subs
I doubt his room is sealed, much less can it be, much less does it matter...
Correct me if I'm wrong....
Sounds like a great room... guess what.... I have the same room only a touch bit bigger, but on the plus side my friend, you do not have a square room or a rectangle room which is in your benefit, the benefit in which you will gain, less issues of cancellation or null's, which means in the end.... Less EQ to get Flat. I started with a single Plus/2 in that same size room and then added a single driver Plus, and it balanced out quite well, but in the end I swapped out that single Plus for a second Plus/2. I have a very good amount of bass now, but IMO, let me restate IMO, its not enough.
Let me add that I have a bedroom setup in a 1700^3 room with a JL F112, and that sub provides me with the slam, impact and tactile feel that I am not getting in my gynormous Great Room.... Not sure what else to tell you, but everyone else's idea's to contact SVS will help you... they will steer you in the right direction. They told me up front that I would likely need 2 Plus/2 or Ultra/2's, but even for me that is not enough... Many would argue, but I am a bass head...
Time for you to start thinking about dual sealed 18's... DIY... they are smaller then a Plus/2... and will kill in that room...
Make them into end Tables...