mega lord
Centre tapped
I started a thread years ago about passive bi-amping, the replies and explanations I got convinced me it does nothing. So decided to buy a better amp. Having said that I know that Bob at Neat used to do it with a Supernait, and a 250; he admits it's marginal though.
One should never take other people's view as gospel, especially the more vocal types who would like to be your guru. Until you have tried it with a certain speaker you will never know for sure.