Active bi-amping is generally considered to offer the best pay-off, but it requires some tech know-how - you need to replace the crossovers (which were specifically designed by the manufacturer for that particular speaker) with an equally effective crossover, then open the speaker and bypass those original crossovers. Passive bi-amping (splitting the pre-amp output with a y-adapter and using two amps to drive one speaker) is easier to do and effectively creates a single amp with a power output equal to the two amps added together (although that may not be entirely true, depending on the amps and speakers). With M200's (which already give you a healthy amount of power), passive bi-amping may not yield much more than either bi-wiring or using jumpers at the binding posts.

What speakers are you looking to get?