Sealed box subs tend to play very deep, but with a nice gradual roll-off at the bottom end. They can play very nicely with natural room reinforcing bass due to this gradual roll-off. From your description, it sounds like boomy is mid or upper bass and not deep bass being overemphasized. Definitely a room placement issue or acoustic issue with your room/seating position. Usually Aud. will tame these peaks in frequency response, but some are too big to fully tame with its equalization.
Start by playing some music that has frequent bass that seems boomy while sitting in your main seating position. Then start moving your head around the room and decide if it's boomy everywhere or mostly just in the main position. If your couch is along a wall, it'll likely be boomy. Near a corner and it'll be worse. The same for the sub itself, corner loading a sub makes them boomy usually, but does help boost output, just not smooth frequency response. Once you've determined your seating position is not to blame, start moving the sub out from the corner or wall. If you don't have a lot of placement options, try rotating the sub's speaker into a different direction. Sometimes subtle changes can help a lot. Othertimes, major sub relocation is necessary for optimal sound.
Another option if you have a laptop and Radioshack SPL meter, download (free) RoomEQ and do some low frequency response measurements to know exactly what's going on. This does take time, but is very rewarding and gets addictive.
Mostly take your time with this to find bass nirvana. Also, careful with your back moving that box around.