Well I would look into these personally I have 5 of them running in my system and they are silent I ternal or external. For the cost I find them pretty good. It all depends on plumbing and size of the drains on your tank how much flow your overflow/drain can handle. Lot of variables in choosing a new pump.
http://www.coralvue.com/circulation-pumps
Probally go for the 700 GPh model
Ehiem pumps are also pretty quiet and reliable.
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360 gallon sps reef, 180 gal sump, bubble king supermarine 300, 4xmp40Wes, 2 x 6215 tunze waveboxes, 4 ghl mitras
360 Reef Tank