"Vertical" biamping

I was going through similar issues with VT100s and my ProAcs, so for an extra data point, I asked the US dist. He recommended horizontal, passive bi-amping. Never got around to tho', since I ended up with a new pair of Martin Logans.

I have been using a vertical bi-amp on my Vandersteen's for about a year. I found it to be one of the most worthwhile improvements that I have EVER made. Vandersteen recommends the vertical biamp over the horizontal. Only one channel of the amp reproduces low frequencies freeing the other channel up for better mids and highs because the power supply of the amp is not bogged down so bad. There is also some benifit to this "unbalancing" of the amps power supply. The only caveat with this is the amps need to be identical with the same input sensitivity(as with any biamp) Vandersteen also recommends NOT using different cables for the upper and lower sections. I can't say if all of this is specific to the Vandersteen speakers. I can say that if anyone feels Vandersteen speakers are layed back and soft sounding(which I hear regularly on this sight), then they haven't heard them set up like this properly. It was amazing what biamping did!

I do not have two of the same amps, so I have to go the horizontal route.
I have two Krell stereo amps. Dan D'Agostino prefers vertical biamping.
I am using The Krell KBX active crossover with my B&W800's and the improvement over just using one amp is staggering! But, remember, I am actively bi-amping which requires alteration to the speaker (Dan D'Agostino designed the change). This was a very expensive upgrade, but worth every cent!
I would consider improving your speakers BEFORE going to expense of an electronic x-over.
Just my opinion
Richard

I use it with my Legacy Classics and a Sunfire Theater Grand amp. It really helped out the sound and the detail. Probably the biggest change was on the low end where the difference in sound was huge. I have tried several times to go back, but can't make myself do it after hearing the biampped version. I would highly recommend it.

You can use an active crossover without removing the passive crossover. If you get an active crossover like Bryston offers where you can set the cutoff point for the upper and lower points separately, you keep most of the unwanted signal from reaching the amplifier, whcih is the approach I would use rather than making mods to the speakers which reduce their value and marketability.