Active Subwoofer Crossover

So in theory, a external electronic crossover provides more flexibility and should allow a more seamless integration of the mains with the subwoofer? Does the external crossover take the place of the preamp or is everything still controlled via the preamp?

I added the CR-1 to my system. I tried the suggested 80 hertz crossover point and it was too lean. I've changed the crossover to 45 hertz and like the overall sound better. The biggest impact in my system is an overall cleaner/ more detailed sound with added space/air...so much so that I'm trying to adjust to what I'm hearing.

I've tried several different crossovers - some active and some passive.  the best sounding, and most flexible, i've found is the XTA DP-224.  one feature in particular that i found has made a significant difference is the ability to time delay the mains.  once the crossover and delays are dialed in, the integration between the sub and mains is absolutely seamless - better even than the vandersteen system, in which the HP filter and the sub amps are purpose built to provide a seamless interaction.

Glad to hear about your decision.  Keep experimenting with the crossover frequency.  80 Hz was really just a starting point, as you discovered.  Room nodes may also play a part in where you finally end up.