I've got the same cpr on my 80, My return pump is a Rio 2700 @ about 700-ish gph. I also have 4 ph's in the tank to help circulation. I have no experience with Mag pumps but many here on the board use them. For my new tank I'm using life guard pumps.
It all depends on how much tank turn over you want your surface skimmer and return pump to generate. A water turn over of at least 10 X the tank capacity per hour is recommended. Many people use a combo of phs' and the return pump to accomplish this turn over rate, or more. I would definately consider the larger sump. More total water volume helps maintain good water chemistry. With the exception of blowing your tank inhabitants around, I don't think there is such a creature as "too much water or circulation."