I know I should do the subwoofer crawl, but my placement options are extremely limited, so I didn't bother.
If you're seating area is in a bass null, turning up the volume, or even putting a second sub in the same location will make no difference. In a null, you have reflections that put sound waves in a given frequency out of phase, so they cancel each other out. Turn the volume up on your sub and you turn up the volume on the out of phase sound wave.
If you can't move the sub, can you shift your seating a little to see if that improves the bass?
