I have a 60 gallon cube with a 18 gallon eshopps sump and eshopps pf-800 hob overflow. Looking at the Syncra SDC 6.0 that has a flow of 530-1450 or the Syncra SFC7.0 that has a flow of 800-1900. My return pipe will be around 4 feet with two 90 degree angles in it. Would you go with the 6.0 or 7.0 turned all the way down, I was just concerned that the 7.0 is to strong.