There is no easy answer... the way that the signal is split also plays a role; is it an opamp xover, tubes or what? This is a critical component. It also matters what the system sounded like to begin with.
IMHO, if there is a big advantage to bi-amping with a system like this it is that you *might* be able to finess a bit of the overall sound by employing amps with suitable characteristics for each range. It would seem like the ideal for this system if it could be tri-amped and if that was the case I'd opt for a set of very clean, and well done p-p 300Bs for the tweets. Depending upon how the bass sounds now, you might opt for finding an amp that happens to have the right "sound" for the room and your ear in the bass region - you can't do that with a full range amp, unless you get lucky. Then in the mids, you'd look for something that is kinda clean, mid power range and dynamic...
The interesting part of bi-amping or tri-amping is that an amp which would otherwise be awful for full range operation *can* be simply marvelous when applied in a limited bandwidth application.
The fact of the matter is that name brand means next to nothing for this... performance does.
