Best subwoffer crossover with room correction

@kykat  - Oh man the prices on the Vandersteen crossovers are out of this world.  I thought they used to have less expensive in-line crossovers. 

You can make your own single-ended crossover with high-end copper foil caps for 1/10th of those prices.  Of course these would only be 6 dB/octave but I'm afraid the prices on the Vandersteen site are way too rich for me.

40 Hz is too low. I agree with Vandersteen that 100Hz is about the right place for a crossover.

It is an unfortunate Audiophile myth that lower is better, but the handful that have tried going over to higher crossovers have learned the benefit.

OP:

By letting the sub take over more Hz you not only reduce the distortion, and increase the dynamic range of your mains but you also make it possible to introduce DSP that is ONLY in your bass. That is, any problems you have in the 20-80Hz range move over to the sub and become easier to manage. 

Done well a subwoofer should make your speakers sound glorious instead of incrementally better.

Lets start with placement.  Use the AM Acoustics room mode simulator to try to find the best location for the speakers and sub.  Try to keep your speakers and listening location out of the worst / lowest room modes.

Next, you should take Vandersteen's advice and use a high pass filter.  Vandersteen sells them directly. Try to use a subwoofer for 10 Hz wide space is madness.  Also keep in mind that the specs are garbage when the speaker is in the room, but many an audiophile who has attempted minimalist subwoofer use has become a convert to using a high pass filter, and one of the main reasons is that it makes integration a lot better and easier.