Which Bi-amp speakers are best?

from the top, working down. then move from right to left. reverse the process if you live in the southern hemisphere.

I'm sorry. I hope I read you correctly. I guess your asking for advise on which speakers to chose which are best bi-amping cndidates???....yes?
Anyway, I guess that would largely depend on what requirements you have for the speakers. For instance, do you need em to play rock and roll?...be full range, etc? Also, I'm not familiar with this model of Meridian, although I've sold it in the past. I'd think the extra set of posts wouldn't give you a true bi-amp capability. But rather just an avenue with which to bi-wire!!! I'm sure itps probably not a separate amplification channel pair you have, but just more posts?...correct? If this is the case, I think the only benefit you'll get is whatever benefits your speakers get from bi-wiring!...?
Anyway, on a bi-amping note, if you do have a bi-amping situation, you'll probably find bi-amping an easier and more acceptable situation with full range speakers, rather than 2 way moitors!(my experiences anyway) And, I mean preferably 3 way full rangers as well, not the 2 way quasi full rangers either! I think what you'll find is that bi-amping a 2 way speaker usually results in way too forward of a pressentation, and often tipped up bright sounding as well! Unless you can find some magical different amp combination to try to balance things out, I think you'll usually end up with not a proper balanced pressentation from the speakers!...2 way's that is. With 3 way speakers, that's a different story entirely..
....Usually, you'll end up with the bottom posts driving a bass woofer on a 3 way, with the top posts driving the midrange and the tweeter!...and usually works fantastic!..usually. Some manufacturers design the crossovers in a what that doesn't always make this work however. Some desing speakers with bi-wire/amp capability (2 post sets), but don't recommend it, as they didn't desing the speaker to sound it's best that way!..you might call a few manufactures first and ask.
However, before you went on your bi-amp quest with that amp, I'd find out if it is indeed bi-amp capable. Otherwis, you might not be ready for the task!
Anyway, if you do biamp, and you don't want to have to get into external crossovers and different amp output ratio's for top and bottom posts and such, I'd suggest looking at some good 3 way designs like B&W 804/803's and such, or similar 3 way's and above! (especially larger woofer candidates! Good luck

The 557 has two sets of binding posts and is dual mono.
200 watts per channel. Sorry for not adding that before.
jazz, fusion, rock...

So, you have one Meridian 557? Then, even with two sets of binding posts, the best you can do is bi-wire, not bi-amp, the speakers. You would have to add another 557 to do that.

In any case, choosing a speaker because it has bi-wiring or bi-amping capability is like choosing a car because it has air-conditioning. It may possibly enhance your enjoyment but it is not an essential contributor to the basic function and quality.