biamp is the best treatmemt for all complicated and tough loads. you might end-up with much less but clip-free power.
you can use
NAD C370 integrated used($400) as woofer amp(upto 600Hz) and preamp --> marchand crossover(tube or ss whichever you can afford certainly with removed speaker crossover) --> your mckintosh amp at upper and midrange.
Many manufacturers would not recommend to go active since it will loose its values but many would state otherwise recommending an optimal crossover point(s) beneficial for amplifiers and speakers together with removed internal speaker crossover.
you can use
NAD C370 integrated used($400) as woofer amp(upto 600Hz) and preamp --> marchand crossover(tube or ss whichever you can afford certainly with removed speaker crossover) --> your mckintosh amp at upper and midrange.
Many manufacturers would not recommend to go active since it will loose its values but many would state otherwise recommending an optimal crossover point(s) beneficial for amplifiers and speakers together with removed internal speaker crossover.