I run an mp10 on my 60g cube and koralias everywhere else pretty much. I like the mp10, but is it worth price tag to me? No. It's a great powerhead but for that much money it performs only slightly better than my koralias, at least in my experience.
I dont think a single mp10 is good enough for a 55g either, I have a 24 inch wide tank and its perfect but to add another two feet to that in tank length and you are probably looking at either 2 of them or an mp40.
180g- Mostly BIG fish and some coral. ~80g Nuvo- My coral tank with "happy fish"~ 90g- FOWLR Not the not happy type of fish~ 125g- Freshwater Malawi Cichlids ~10g- Nuvo- The refugees from the Ich of '18