bi-amping components correctly?

You don't gain the key benefits of bi-amping if you still use the passive crossovers. 

Some folks, DYohn included, like the voicing of passive crossovers.  Cool, great, wonderful.  I have absolutely no arguments against that.

However, this is NOT the type of bi-amping the Elliot article and others about true bi-amping are talking about.  Again, if you use the passive crossovers you lose just about all benefit of bi-amping. 

(Unless you do some sort of hybrid thing like haemphyst was talking about on that linked post.  I've never tried anything like that, so I can't speak to how effective it is.  My knee jerk reaction is that the different crossover points and the both active and passive crossovers might cause some phase problems that interfere with the very voicing we're trying to maintain... but I'm a noob when it comes to passive crossover design, so I'd like to hear DYohn's, Stevdart's, and Haemphyst's opinions on this).

This is a good discussion.  In general, here's my opinion.

For car audio where the gear is relatively cheap and available, it is easier to use a full-active system.  Although I am a proponent for passive crossovers (and it is their "dirt" than gives them much of their character!) in cars it is easier to setup and easier to get 'right" to use active crossovers on the pre-amp side.

In homes and in HT, I prefer to use passive crossovers with bi- (or tri-) amp setups.  It can create a much warmer (i.e. dirty) sound and you can compensate for specific driver shortcomings with a few clever circuit tweaks that are simply not possible - or not easily possible - with active crossovers.  In cars these little peaks and valleys are largely not noticable since a car is a terrible place for critical audio.  But in a theatre they jump out and smack you on the head, so passives are the better choice to compensate for them.

Damping Factor = (Load Impedance) / (Output Impedance)  load Impedence is the loudspeaker SYSTEM Z and Output impedence is the output impedence of the amplifier (usually normallized at 1Khz.)  Load impedence is the total load presented at the amplifier teminals, including crossover, loudspeaker voice coil(s) and speaker wire.  DF has no real meaning above 1200Hz..

Damping (AKA cone control) is critically important in low-frequency systems where accuracy is the desired outcome.  Too low DF will result in "flabby" sounding bass with a LF rise in both impedence and distortion and loss of definition below about 100Hz.  A completely un-dampened speaker system will easily exceed the woofer's mechanical limits and cause it to "bottom out" and can fry a voice coil.  HOWEVER, a damping factor of 10 or greater is really all that is needed. 

Since even the crappiest car stereo amplifiers have output impedence of no more than 0.25 ohms, a load impedence of at least 2.5 ohms creates a DF of 10.  Higher load impedence and/or lower output impedence creates better DF.  But paying a ton of money (or sacraficing power utilization) to create very high DF numbers is largely meaningless and a waste of money.

Did I suggest that one article was different than the others?  I threw the modifier "true" in there simply to distinguish it from the "bi-amping" that home audio manufacturers talk about with their 5-way binding posts that still use the passive crossover.  I wasn't trying to say anything more.  I realize that wasn't the greatest sentence in the world - I didn't get much sleep this week. 

Very nice explanation.  I haven't seen the above paragraph said so succinctly.  I've also seen the articles on damping factor you posted. 

So, here's tangential question for you all that I've been curious about.  If damping factor doesn't matter, and if tiny levels of thd are inaudible, what other criteria should be looked at to evaluate amplifiers?  Intuition tells me that next to nothing is gained from buying very expensive amplifiers.  Is this true?  How and in what way do expensive amplifiers produce better quality sound?