The article Smart Reefs by Jake Adams in last months Coral magazine recommended no more than 4 times your display tank's volume per hour. For you that would be up to 320gph. I personally just went with the first pump that I found a good deal on. Nothing about my tank is very energy efficient (or well planned)... Maybe the next one will be.
http://coralmagazine.coverleaf.com/coral/20100304#pg3
This article recommends 3 to 5 times the display tanks volume per hour.
Reefkeeping 101 Sumps!
http://reefkeeping.com/issues/2008-01/newbie/index.php