Duke brings up some very good points. Adding multiple small subs is beneficial, as it will smooth out the overall response. Unfortunately, adding more subs brings its own problems...and that is getting them to blend invisibly into the mix. Not to say it cannot be done, as I have managed this in my room, but it is more difficult to achieve and will take a lot more effort...and patience.
I wouldn't go with the headphone suggestions...no need to.
Since the room measures well and has a high ceiling, I think you are fine.
I wouldn't go with the headphone suggestions...no need to.
Since the room measures well and has a high ceiling, I think you are fine.