gonk,

I sent you a PM!

If you are using bi-amplification without active crossovers ahead of the amplifier and are still relying on the internal speaker crossovers, then any attenuation that the loudspeaker manufacturer built in to the crossovers, in order affect the ratio of signal sent to each driver, still remains in the signal path. Sending one amplifier channel to the woofer and another amplifier channel to the mid and/or high frequency drivers through the original crossovers merely requires that both channels have the same amount of gain/output – unless you are using channel gain as a substitute ‘tone control’ in order to create a different ratio than the manufacturer intended.

While idealistically I prefer active crossovers ahead of each amplifier channel and the elimination of the passive crossovers, the implementation of such a system is much more involved, technically and financially.

I use unbalanced runs, generally of 2m or less, without problems. I use longer unbalanced runs, about 5m, to powered subs without problems as well. Most of the interconnects are constructed of a rather high-quality commercial cable, Belden 1694A. A few cables, for the rarely used VCR, are RS next-to-best grade.

What is a "long distance" that would justify balanced cables? 7 feet? 15? 20?

Speaking of Soundhound, I think he used to consistently argue against the use of balanced cicuits except in very long runs (> 50').

It depends on who you ask, and on the environment. I wouldn't consider 7 feet of interconnect particularly long (that could just be from top to bottom of an equipment rack).
Soundhound had some very reasonable and sound (no pun intended) arguments against balanced connections outside of the harsh environment of a recording studio (the type of space for which balanced connections were developed in the first place). This arguments can still be seen in a couple of old threads (start somewhere near the bottom of this page for the most lengthy debate and then move on to this thread as well). He runs unbalanced from his equipment rack to his amp closet, which would likely equate to cable runs of 20' or 25'.

I do some small sound work for bands, musicals, etc. as a hobby and have run unbalanced in some instances as long as 100 ft without any problems. But balanced is better in that instance because it would reduce any common mode noise. Depending on how it is designed, balanced also gives an instant 3db increase in signal to noise ratio just because it is balanced regardless of cable run.
My system is all unbalanced at home, and balanced for my sound work.
The one exception is all my sound restoration work is done with equipment all balanced (where possible) up to the time it is digitized. I want that extra noise reduction.