How many gph on powerheads for 90 gal?

[Oxymoron]

Hello all,
I am going to install 2 powerheads into my 90 gal and was planning on going with the Koralia 3's or 4's (headrd they were one of the quietest). Was wondering how many gph per pump is suitable for the tank size.
Am wanting to buy something that would suffice for any kind of coral growth thus never needing to be upgraded. (at least for a while anyway)