go with the Mag a rate of about 10x turnover is pretty good unless you are going to have a fudge in the sump then you may want to slow the flow down in the sump or you could recalculate some of the water flow back to the sump it would give the slowed down effect. I have allot of movement in my tank but slow in my sump as I have fudge in it too. I also have a little giant external it has some thing like 895 gph with a vertical lift of 18 feet this pump will be on my 90 once in is up and running

Bill