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

It’s not a waste. Assuming the passive crossovers in your speakers are good, you still gain the benefit of having separate amps for each channel, which have similar benefits as monoblocks. There’s better physical and electrical separation.

Are you driving the woofers with one side of each amp, and the tweeters with the other? (ie: one stereo 2 channel amp per side)

The benefits should be more about soundstage and separation improvements than any tonal balance changes, but in theory there could be some clarity improvements too. The improvements you may hear are a variable that depends a lot on the rest of the system. What are the amps and the speakers?

There are pros and cons with every choice, and few absolutes. Active crossovers and passive crossovers each have their pros/cons. Most active crossovers can’t address problem areas within the drivers like passive crossovers can. They only act as high, low, or bandpass filters, no notch filters, no shelving networks, no zobels, etc. Hook an active crossover to a driver with issues, and you can have a mess that can't be compensated.  A really good passive crossover with high quality parts can sound amazing. Passive crossovers can be more complicated to design well, and many use cheap parts that effects performance.

I’m taking sort of a hybrid horizontal approach . Tube amp monoblocks on the mid and tweeter with passive crossovers, then an active crossover to an integrated solid state amp that just drives the woofers @ ~ 80hz and down (and the active subwoofer).

Two identical amps....one for each channel has less crosstalk, and a dedicated power supply on each channel....similar benefits as mono blocks. Any amp should benefit from that scenario.  If you use two identical stereo amps, you can use one channel for the woofer, and the other for the mids/tweeter on both sides.  A channel that doesn't have to deal with the stress of driver a woofer is usually going to be better...how much is audible is an unknown, but its a better situation for the amp.  I don’t see it as a total waste at all. It can really improve the soundstage, and dynamics of a system, and sometimes clarity other characteristics, depending on other factors. How much improvement you can hear depends on many things. It may not be worth the improvement to spend a lot for another identical amp, but if you already have them, or can pick up another at a reasonable price, there’s definitely some benefit.

Link to a diagram that may help:

https://www.audioholics.com/frequent-questions/the-difference-between-biamping-vs-biwiring/HorizontalvsVertical.jpg/image

@lonemountain

There are pros and cons with active, and with passive crossovers. In a perfect world, active crossovers have some distinct benefits....especially if starting up from scratch, but many of us get to the bi-amp situation once we’re already well invested in our current systems. Sometimes it just not feasible to backtrack to square one.

@unsound reiterated some of the benefits and situation need for passive crossovers. There are certainly active crossovers that can perform some, if not all, of the compensation requirements of some drivers, but what if you already own a really nice pair of speakers that you love and that have excellent, well designed passive crossovers with top shelf parts, and you want to dip your toe into bi-amping? I’d think even a serious audio buff would hesitate before proceeding to gut the crossovers from a pair of Magico, Wilson, or Sonus Faber speakers so they can experiment with active crossovers. Not everyone has the knowledge, expertise, or the will power to actually make such a bold move.....in many cases it’s simply not wise to risk the destruction of a wonderful pair of speakers to pursue an active crossover. If a great pair of speakers sounds good with passive crossovers in a single amp situation, they’re very likely to sound even better with a good bi-amp setup, even with the passive crossovers.

@lonemountain

Why no comment about all the wire and passive components between the amplifier and driver ? ...

I’ll take a stab, but can only speak for myself and guess on behalf of others. If you own a pair of speakers that you love, or simply won’t part with, that have passive crossovers, removing the passive crossovers is likely not an option, so contemplating the amount of wire in the crossovers is likely just a moot point.