Specs on Sump 4
Overall Dimensions 38-13/16" x 15-7/16" x 19-17/32" high
Sump Dimensions 38-13/16 x 15-7/16" x 15-21/32" high
For Aquariums 125 to 265 gallons
Max Flow 1,400 gph
Intake Dual 1"
If you plan on running all of the overflow water through your skimmer your pump will need to be matched to that flow.
Unfortunately not an easy answer without knowing what equipment you would be using and what sort of pluming will be used. I usually pick a return pump based on the number of devices I plan on running off of the one pump (skimmer + phosphate + UV + head loss etc...) = the overflow rate desired. Circulation within the tank is better attained using power heads, wave makers, closed loop...etc
Keep in mind that if your flow is too high you can always bypass back into the sump, however inefficient, but if it is too low you will need to upgrade or add additional pumps.
All that being said have a look @ these
Eheim 1262,
Danner Mag-Drive Supreme 9.5