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 Reef - 60g Rimless Reef -90G FOWLR- 125g Malawi Cichlids- 40b REEF- 34g Fresh Planted-working on- 20L FOWLR- working on
I have a mix of many different saltwater fish amongst my tanks, but I love my Tangs most of all.