After years of having done it both ways,bi-amp with stereo amps vs single amp,I think a very very small sonic benefit exhists with bi-amping.The greatest "benefit" to bi-amping I would say is easing the load . I have never tried mono blocks and was wondering how that sounds compared to stereo bi-amping .Note....This is passive crossover not active .
Depends on the gear. Some mono blocks are good, some bad.
The good things about mono blocks is the seperate chassis per channel and seperate power supplies.
Have you tried vertical bi-amping?