I did a closed loop on my system here....And im very very happy I did. I got alot of ideas from Melevsreef .
Here is a couple pics of my system, I built my own sump and im using a mag 5 in it, so im getting about 3x turn over through my sump, and my CL is on a Dart 3600gph pump....and it couldnt be quiter!
Here you can see the pipe with the T fitting is the suction, and the return gets split up between 3 Dual output Lock Line outputs.
The tank has only been up a couple of weeks, but so far no problems at all with it, and the noisiest part about the whole setup is the ASM G2 skimmer....So its pretty dam quiet