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

Yes. I have XLR Y-cable splitters. It comes out of my preamp splits the channel and then each of those goes to a channel on the amp. 
 

My preamp (Marantz 8805A) has a bi-amp mode in the setup menu that allows me to use another channel for bi-amping. They claim setting it up this way and I'll quote from their explanation: 

FROM MARANTZ

"This connection enables back EMF (power returned without being output) from the woofer to flow into the tweeter without affecting the sound quality, producing a higher sound quality."

But for some reason unknown to me when I use this method of connecting my XLR cables and run a level test in the setup menu. When the left speaker is putting out a test tone I'm getting both main speakers playing at the same time the high frequencies and when I switch to the right speaker I get both the main speakers low frequencies playing at the same time. Not sure if Marantz implemented something wrong here or not but I don't understand it all. So I connected back the XLR splitters. 🤷🏻‍♂️

I experimented with bi-amping Magnapan 1'6's with two Arcam Alpha 10's. I really couldn't hear a difference. I went the next step and added a Bryston 10B active crossover removing the passive crossovers with a custom speaker terminal. Huge difference in everything for the better.

FWIW - Maggies are known for their simple and somewhat cheap crossover components, so as others have said, the conversion to active might not be as simple or as fruitful in other systems.

Jim S.

Unless your amp in inadequate, 2 identical amps is a total waste of money.

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.