What are your existing Class A mono amps?
From my experience, biampimg different amp brands often don’t produce desired results. I am currently using a Class D / Tube amp setup without an external crossover. It wasn’t easy and against all odds I have managed to mate the two amps in perfect harmony.
More details / advise to follow once we know the spec of your Class A monoblocks.
I hope @almarg chime in here, he was a tremendous help to me.