Big enough pump?

[bluesox68]

OK so I bought my system used and the return pump is old and noisy, It pumps from my sump to a T it seperstes to a reactor and to the DT I can't identify the name brand of the pump but its about the same size as the new quite one 4000 I have new. The distance from the 20 gallon sump to the 40 gallon tank is maybe 3 to 4 feet? http://www.marinedepot.com/pumps_pen...et_one-ap.html Without know the gph of my old pump could you guess if this would be similer or better? I really want to know if this new pump will work with my system Thanks!