Honestly I would try that first, I know reefflo pumps are meant to push a lot of flow but not to pull any water in. You are lucky that you have an acrylic sump, I had to pull the sump out just to punch a 2 inch hole to accomedate my reefflo dart. Keep me updated. Have a good new years.

Well I re-plumbed the intake to my pump today & also added some sound dampening pads under the pump as well. I think it is a little bit quieter then it was before but will not really know until I go up to bed, if I can't hear it then I will be a little bit happier. Update in the morning.

I had the same problem as you, was getting nasty resonance and driving me crazy, I installed rubber couplings on the intake and returns right where they enter/exit the pump and installed damping pads ( from Sears, intended to go under washing machines) and it made a huge difference to the sound I was having. Changing out your intake to a larger line should make a big difference for you as well, restricting the intake can cause cavitation and vibrations.

Changed the inlet today to an 1.5" but still have a little reverberations coming from the pump. Next step is to change the outlet side to an 1.5" tee into 2 - 1" lines with rubber hose but maybe not until next weekend.

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.

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

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.