Is it best to use a 5-channel amp for biamping??

Arthur- IMO using 4 of the Krell's channels should make a difference. I'm assuming the B&W's bass & mid-hi x-overs are discrete (not connected) of course. You should have better control and response in the low frequencies.
Planckscale- sorry for regurgitating what was obvious to you!
Cheers

Thanks gentlemen!
Luis

Greg,
Don't mention. I appreciate your input.

Let's take the discussion a step further. If I were to split the signal at the amp, and rather than use 2 of the channels on my Krell, use one and run the other side of the split to a tube amp, what type of things would I need to understand in terms of power, crossover, etc., to appropriately match a tube amp to the mid/high connections, and my Krell to the woofer?

But for hybrids like MLs, which Planckscale has, passive biamping has significant advantages.

Passive biamping an ML hybrid separates the stat from the woofer, thus presenting the amps with a less complex load.

The stat panel presents the amp a high impedance at low frequencies and very low impedance (1 to 2 ohms) at high frequencies. The woofer's impedance curve is relatively more flat. Driving them separately makes the amp's job much easier.

I biamp my Aeons with four of the five channels of my Meridian 5-channel amp. This makes the speakers more dynamic - a frequent complaint about hybrids is that they're not dynamic enough.