Need to know what is the quietest & highest GPH return pump

[Big Tang]

Just use a six inch piece of spa flex on either side of your pump (intake/outtake )and that should look after any resonance from your pump that's what I do for every reeflo I install.

[The Grizz]

Already have spa flex on the outlet side and have no room for it on the inlet side.

[RuGlu6]

Have you considered water blaster pumps?
Silent and push a lot of water.
2600gph both internal/external
3 year warranty from Coralvue.

http://www.goreef.com/Water-Blaster-Pumps
However i have never had one so no first hand experience.