Hello,
I am new to the hobby and am just setting up a 125 gallon tank. I bought a Dolphin DP 900 pump and set it up with water, etc this week. The pump is very strong and extremely quiet. We can't hear it at all. We did intall it as a submersible, inside the sump. I don't know how it would sound outside of the pump, but they claim to run quieter and cooler than other pumps.
Might be worth a look.
Good Luck.
-Christine