My experience is similar to Jeff's. I find the better the main speaker is at plumbing the under world , the better, easier and faster it is to integrate a sub. My Apogee Slant 8s go down to a solid 25 HZ in my room and I was quite satisfied. Then I auditioned a used Velodyne FSR-12 that a dealer had for a very good price. Using the internal x-over from the Velodyne for both the high pass and low pass functions, I dialed the critter in in only about 30 minutes of tweaking. What a difference! With the bottom end of the Apogees rolled off below 80 HZ, they could play insanely loud. Got rid of a nasty mid bass peak in the room, and had a more transparent, larger and better defined soundstage too. The bottom end was deeper (actually got that last 5 HZ), tight as a nut and positively thrilling on some stuff. Definately worth the $700 I paid for the sub and it definately complimented the main speaker.
Great sound possible using a Subwoofer?
My speakers are flat to 38 hz but I feel I'm still missing impact, power and weight on most of the pop/rock CDs I listen to. I don't know if a high quality subwoofer would be a positive addition to my system or just add unrealistic bass and muddy up my midbass and midrange. If anyone has extensive experience with this dilemma please tell me what you think. (would better isolation of components, cables or power conditioner help the low end?)