Am I wasting money on the theory of Bi-amping?

Multi-amping could have advantages even if done before the cross-overs, and even more so if each channel has its own power supply.

If a speaker has a challenging impedance / phase angle above or below the frequency range of the cross-over the amplifier will often run with more strain and corresponding deviation from ideal performance at these points. A single amplifier channels performance can be dragged down across the entire frequency range by these demands, where as multi - amplified frequency ranges will only be compromised at the particular point of the challenging load, freeing up the other ranges to be powered more optimally. This might be especially true in cases of so called Class A/AB amps where more of the more optimum purported Class A bias will be allowed to run longer before resorting to the less optimum purported Class AB or Class B (these classifications are somewhat nebulous, but the results are somewhat the same).

That these challenging impedance / phase angle loads are more typically found in the bass region where the power needs are greater but where our hearing is usually less sensitive, so meeting the power demands might be more important than ultimate fidelity. On the other hand the power demands of higher frequencies ranges are typically less, but our hearing is usually more critical, and the greater purity of amplification is appreciated more.

Bi-amping is not a "theory" neither are bi-(or tri)wiring. You just need to know what you are doing. Results will depend on the quality of the involved components and als the chief`s skill-level.

Some speakers has terrible passive filters, like the famous old Infinity Kappa 9. Bi-amping won`t solve this, but bypassing the passive filters and instead using an active filter would do. 

If one were to bi-amp with a tube amp for the tweeters and mids, and a SS amp for the woofers, how does one volume match the signals since these are different amps with different gain?  Even if the same wattage the two amps might not be matched?  Thanks. 

I had A pair of speakers that responded well to a krell kav300il on top but needed more juice for the bass. In that case horizontal biamp made sense. Starting from scratch I think I’m getting great sound with a pair of matching monoblocks 1 per channel and if you get powerful enough amps you should hear what the speaker designer intended. My current system Kef Blades has a fairly bumpy resistance so the Mac Mc611’s really get it done. The speaker amp combo can make or break your system.

The very basics: a [speaker] passive crossover comes AFTER the amps, operating at speaker level.  The drivers are connected to the crossover not the amplifiers; active crossover /electronic crossovers come BEFORE the amps, operating typically at [balanced] line level; the drivers are individually and directly connected to a specific amp channel that is for that driver and that driver alone.  

It is hard to understand how anyone could think shoving a bunch of passive electronics with lots and lots of wire into an audio chain between the amplifiers and drivers could be a step up in quality and create a better, more pristine audio chain.  I wonder if passive fans realize how much wire is in an air core inductor used in a high quality passive crossover (300-500 feet or more?).  We don't do any other processing after amplifiers, why is the passive crossover somehow an exception?       

There is so much science here that is quite established and well accepted, since the 60s-70s at least.  ATC and Genelec were offering full [analog] active crossover loudspeakers to the market in the early 80s, some with internal amps, some with external amps.  Both companies sold into home and pro simultaneously.  Now there are many more companies offering active crossover speakers and some use DSP, some still analog.  

There are plenty of options and choices as to how one can approach this active issue and adapt it to your liking, make it sound one way or another.  It does require some work to understand what is happening, but its certainly not complicated.  It is not more expensive or more difficult to operate.     

I cannot help but observe the entire "passive crossover is better" argument appears to be a clear example of marketing not science.   

Brad