I've heard great things about the quiet flows as well...but sometimes you just have to save a couple of bucks.
I really like my Mag 7. I have a ball valve installed so I have the flow exactly how it needs to be on my tank, and without it pushes about 700 gallons per hour. I don't remember all of the original math behind it, but it fit the bill on my 55 gallon tank and 20 sump when compensating for head loss from the HOB
overflow on the system and length of pipe on the system.
Here is a head loss calculator if this is of any assistance.
Darcy Weisbach - Head Loss Calculator, Online Calculators