4 amplifiers to drive 1 pair of speakers?

This doesn’t make sense to me. Not trying to be rude.

When you say the speakers are more like 4 ohms in real life, you’re saying the impedance swing occurs with changing frequencies, which is true. However, A well designed speaker at 8 ohms uses quite a bit less current. Impedance may swing to 4 ohms every now and then, but it will not remain there for long.

I don’t think you would need a power amplifier. That’s probably overkill. An integrated amp that is pushing about 40 watts per channel or more at 8 ohms will do fine. Vintage gear that was made in Japan is probably the best value.

Last thing - on the back of any speaker amp you’ll see something like:

8 ohms - 16 ohms
4 ohms - 16 ohms

Lower impedance = more current required.

@thegreenman.... You are correct to worry about Impedance dips.  It does somewhat matter about where (what frequency) they are, but the real problem is to try to get an impedance/phase sheet on your speakers.  Normally impedance dips are accompanied by phase angle dips.  This is where many many tube amps crap on themselves.  
I read that each speaker had 2 binding post?  So yes, assuming that you are running them as mono's, you could conceivably run your  amps that way. 

Well, you should try it first. :)

But active bi-amping may be a much better way to go.  Use a solid state amp for the low end.  Put a capacitor in series with your top end amps.

THe thing about passive bi-amping is your amp still has to reproduce the full voltage swing (+ or -, corresponding to in/out on the speaker).  You do reduce the current, which stiffens up the amp, but if you can remove the bass from the amp the full power becomes available for the high range.