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

I have two NAD M23 amps and speakers are Paradigm Founders 100F. 
 

I am using them in a vertical bi-amp configuration. 
 

I have four subwoofers handling the very low end. So the amplifier shouldn't be stressing out in any way. Even when I had just the one M23 amp connected using both speakers it sounded phenomenal. That's when I decided I wanted two. I loved it!
 

The amps can be bridged but I felt this could degrade the quality of the amp and chose the buying of two amps instead kind of like a monoblock setup. I've usually used monoblock amps for my system but NAD doesn't make a monoblock amp in this M23, even though it can be bridged I just felt bridging could degrade the quality l heard when connected in two channel. 
 

I've never tried bridging these amps but based upon Audioholics testing said it did kind of decrease the quality over running two channel mode.   
 

I'm just trying to learn more and appreciate the feedback knowledge!

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. 🤷🏻‍♂️

Alright found out some information about my preamp and the bi-amp mode it has.

It’s pretty neat when turned on.

Within the preamp (setup in the setup menu) and before the amp, the preamp sends out each channel as a high and low signal (two channels for each speaker and a total of four channels for two HF & two LF signals). When connected properly the LF channel doesn’t receive a HF signal and vice versa.

What Marantz does is separates the one channel for just low frequencies sent out and another separate channel for just the high frequencies. 👍🏻