Passive biamping will not help you. This speaker has no business being designed with passive crossovers. It should have been designed with active crossovers and built in amplifiers.
As I have pointed out many times before, designing passive crossovers at 80 Hz, as in this speaker, is a dead end, and should not be done under any circumstances.
When you calculate the load the amp actually sees from the impedance curve and phase, it is 1.6 ohms at 20 Hz and 1.5 ohms at 70 Hz.
Worse, I would bet that those numbers are lower than the DC resistance of the drivers, which would indicate ringing at the 80 Hz crossover region.
In my experience this is pretty much the rule in this type of approach.
I expect these speakers have blown a lot of amps. I doubt the EMO is robust enough for this speaker.
If you want to keep these speakers, I would recommend Quad Current dumping amps. These are unconditionally stable under all loads. In my view they are the finest and best amps available for domestic audio systems.
The 909 can be had on eBay and Audiogon for under $1000.
Or you can buy its replacement, the Quad QSP for around $1800.