Is bi amping worth it ?

OP:  

I jumped into the discussion about biamping without reading your original text. I think it is smart to step back from purchasing a subwoofer without fully understanding the implications.  

I'm not sure bi-amping will give you enogh benefit, but it's not a zero gain solution either.

An intermediate and often overlooked approach is to improve room acoustics. An overly reflective room will "lack bass."  The real issue isn't that there's not enough bass but that the mid-treble stays around too long and raises our perception of mid-treble output. 

@roadcykler 

There is no objective difference using 2 amps instead of one. There are no speakers that can differentiate where electrons come from. 

While I can’t often justify passive bi-amplification’s cost, I have to disagree with your statement, somewhat.  @ditusa posted a paper from Lansing Heritage which may seem very old but some still has merit today. 

Your statement would be true IF every solid state amplifier were a perfect voltage source but they are not.  The behavior of each amp when providing current varies significantly. 

My experience with amps and speakers and as a speaker builder and investigator lead me to believe that bi-amplification could have measurable benefits. 

In my mind, the issues come from the tendency of speakers to have dips in the impedance curve, especially at the mid bass.  By dips I mean anything less than 4.00 Ohms.  I think these dips are audible, even with a typical modern SS amp with high damping factors.  I think in some cases speakers are even deliberately tuned to have a dip so they are more "discerning" of amplifier "quality." 

These impedance dips can lead to a softening of the DC voltage rails, and provide a path for intermodulation distortion to creep in.  By having a separate amplifier for the "high impedance" part of the speaker you eliminate the bass current draw from modulating the rest of the output.  

Next, there’s the issue of total power demand.  While passive bi-amping does not change the expected voltage swing of each amplifier, the current draw of each amp, and therefore the power, does get reduced significantly due to the high or low pass filter’s increasing impedance away from the crossover point. 

Having said all of that, from a pure efficiency and cost point of view, active bi-amping spanks all of those for benefits of current and power delivery.   Another approach which I feel raises the value of bi-amplification is to use flavorful tubes for the mid-treble and solid state for the bass.  You get the best of both worlds, while eliminating the impedance matching issues of tube amps.   If you put a single cap in series with your tube amp you can really get outstanding dynamic range improvements.