i will partially disagree that bi-amping is a WOT without a crossover before the amps. Most midranges and tweeters require modest power, but that's where all the delicacy resides. Its much harder to reproduce a ~20,000 Hz complex wave than a ~20 Hz complex wave (~ since complex and one freuqency are contradictory). They can be served well by modestly powered, sweet sounding amps. Tubes if you like. or a nice class-A amp.
OTOH low frequencies demand low output impedance, and high power. Delicacy on a large, low-Fr wave is somewhat irrelevant. So a honkin big solid state power amp is ideal.
Doing that - even when using the internal crossovers can be useful. Admittedly i have amps coming out my ears ( i design them, and years ago made them) and even i don't bother.
I do agree that a crossover between the pre and the two amps, along with control of gain, is better still.
G