IMO, if you're running a skimmer, its useless to have more GPH than your skimmer pumps can handle. Any more flow through the sumps is water that is getting by without being processed properly.
Also, slower flow through the fuge is always better. More contact with our little fuge buddies and the media/marco the better.
Here is some good reading from a member on here. Mr. Wilson in regards to a very nice 1350 gallon tank in canada.
http://petersfishtank.com/best-practices/#w.flowsump