[Wayne A. Pflughaupt]

Well, I'm actually pretty satisfied with the sound, but am missing that bass that can be felt. Since my current sub isn't all that small, I was wondering what it would take to really make a difference - the answer seem to be "a lot"..

I'll concur with everyone else that you really don't have any huge problems. That said, many of us prefer response that remains flat below ~30 Hz, rather than sags. Marc's recommendation for filters appears to be a good starting point. Where is the sub located? I can't tell from the picture. You might try different locations to see if you can deal with that ~45 Hz thing. If it's in a corner, try moving it down the wall a few feet - sometimes that can make a difference. Another approach to finding ideal placement is to put the sub at the seatng location and move the measuring mic to prospective locations. Much easier on the back.

Regards,
Wayne