If you got another one, the benefits would depend on where you place it. If you placed it right next to the one you have now, you would gain a 6 dB increase in headroom. If you placed it in an adjacent corner, you would likely gain a flatter frequency response and also better room coverage, so you get a more even bass sound throughout the room, but only a 3 dB increase in headroom. You could also do things like place one near and the other far, so you can get different emphasis at different parts of bass.
What mains do you have, btw? Did you really set the crossover at 50, or did you set the mains down to 50 and keep the sub at 80 or higher? You have to realize that with the crossover at 50, that is a harder load on your receiver, but it is probably ok.
One thing you can do is get another sub, place them next to each mains, and raise the crossover to like 100 or 120. This ought to give you some massive mid bass, and because you have the subs right next to the speakers, you don't have to worry about bass localization where sub is drawing attention to its position.