Wow - thanks for the very insightful replies.
My system is a Denon 2900 player as a transport into a Lexicon MC-12 pre/pro, into a Krell FPB-200c for L/R (I listen to all my music in 2-channel), into Dynaudio Confidence 3's, with a Velodyne DD-15 sub. Speaker wire is heavy-guage copper, no brand.
Room is 14x19x8. Speakers are about three feet from side walls, 4 feet from rear walls.
The sub is in the front of the room, behind the speakers. The Velodyne comes with on-board equalization and a microphone to calibrate with - I am able to get a smoother response over 20-200Hz with the equalization, tho not close to perfectly smooth. I moved the sub around the front of the room and got basically the same response curve.
Regarding integration between sub and mains, and the occassional "over-hot" song. On most music (I listen to rock, jazz and blues, primarily), the integration sounds really good - the bottom end is there much more authoritatively than before the DD-15, and it is really well delineated bass - you can differentiate the notes being played, and it really sounds like an instrument rather than just low freq. energy. Much, much better than an older, cheaper Velodyne I used to have in the system. Thrilling, actually. However, occassionally a song gets played where bass is sort of overwhelming - usually on something like a modern R&B album. Even at moderate levels, the house seems to suddenly be shaking, and the bass dominates the music. I have attributed it to recording engineers who want this type of music to sound impressive on less-than-impressive systems. It could be a set-up problem too, I suppose.
Thanks again for the help.