Main circulation pump and filter question

[1stMarDiv]

Our 120 gallon tank main circulation pump is getting really loud and I think we should be changing it out before it dies. Haven't bought one in about four years and heard there are some really nice ones out there that make hardly no noise running. The one I have flows about 1100 gals per hour. I was thinking I should maybe step that up a bit? In conjunction with this timing, we are also planning on installing a newer improved sump in the next room and discontinueing the 65 gallon sump below the tank. The new sump is 48" long by 18" wide and 24" tall. We have deep sand beds and only an AquaC 189 skimmer for filtration. The tank has been set up for several years and all the parameters test fine. However, we have been dealing with an algae bloom which we think is a product of the live rock being in the tank for several years and having decay trapped in it. We thought maybe we should install a mechanical filter in line this time, that we can install various filtration bags to help us remove whatever from time to time. Maybe at times just leaving it empty. Does this sound like a good idea, and what recommendations do you have regarding the main pump replacement? Thanks for the help. We want to make this upgrade worth our while. We plan on chambering the new sump tank with plexi panels, with the first chamber having live rock on a bed of sand. The second chamber will have more sand and our protein skimmer, and the third chamber will be just clear. Any ideas or help here will be appreciated.