Good point about considering a better subwoofer, which in turn I can also use with my box speakers.
@johnto Yes, I have it setup at around 55 Hz and volume as low as possible to avoid boominess. I used a spectrum analyzer on my iPad to help with the adjustments. I have two listening positions, the sweet spot and the "comfortable" spot, and unfortunately the sweet spot has a null at around 60 Hz, and the comfortable spot is a bit boomy with the sub :(