How big a room are you using it in? Here's why I ask (and please excuse the long-winded anecdote
My previous sub - an SVS PB12-NSD - was a wonderful sub for movies, but I found it to be a bit lacking for music. Part of the reason, I believe, had to do with my HT/music set-up being in a ~3,375 cu.ft. basement room.
While the sub wouldn't get boomy (although it was a touch on the "flabby" side), like you, I found that I would have to boost the bass for music, and drop it back down for movies.
My upgrade to dual ChaseHT SS-18.1s just over a year ago - primarily to get a bit more output for HT - resolved the music issue. My subs are integrated into my system, everything is calibrated, I run the subs ~3-4dB "hot" for movies...and I never have to adjust the level for music. They're always good.
(Actually, that's not entirely true: On really bass-heavy music, I may have to dial the level down a dB or two. Otherwise, I never change it.)
Perhaps, in your case, a second Lava sub might give you that extra grunt that a single sub isn't delivering? Perhaps moving to a larger / more-powerful / sealed sub is a possibility?