Agree with those who say that you really have to have an active bi-amp system for it to make much sense. Some benefits can be achieved with a passive vertical bi-amp which of course assumes you are using two identical amps. Otherwise, you need an active crossover. In my system,
active crossover low passes the bass below about 8O hz to a high power
class D stereo amp then to a pair of 10" woofers for each channel; and high passes the mids and highs to a tube amp that drives the (almost) full range drivers. This does introduce lots of complexity and requires lots of outlets and cables. The system to my ears sounds wonderful but there are many places for gremlins to rear their ugly little heads, which per Murphy, happens on occasion.
In my case, the music I listen to does not have an overwhelming amount of very low bass content so most of the information is reproduced by the tube amp. The class D amp is really for all practical purposes, a sub-woofer amp and in fact, the active crossover I use (NHT X-1) was designed primarily to use ahead of a subwoofer.