Biamplification vs. Bridging Power Amplifiers - page 2
Conservatively, let's only add 1 dB for the improvement in
woofer output due to elimination of the woofer series inductor
in the passive crossover. The tweeter is capable of an average
output from 6-8 dB in excess of the woofer, and the phenomenon
of masking will allow the tweeter to cover up the woofer
clipping by at least half of that, or 3-4 dB of additional
output before the output becomes noticeably distorted. Again,
that is a conservative number. That's at least another 4 dB
total increase on top of the nominal text book 6 dB for
biamplification, or a total increased SPL over the single
channel use of 10 dB.  As far as reliability is concerned, the
tweeter is only exposed to 100 watts of power capability, not
400 watts, and the same goes for the woofer. Accidents or sudden
overloads are much less likely to damage a driver, and the
amplifier is likely to be less stressed than when in bridge mode
operation, which does add some extra operating stress.