This day in age, a quality AC pump will run roughly the same as a standard DC pump. To respond to the therapist: I personally have the new generation Jebao Sine Wave pump and I cannot give it enough praise, it's quiet and has an incredible amount of torque--even at low power. I'm using a DCP10000 on the lowest setting in my Reefer450 and it's more than enough flow whilst drawing 19 watts. As for reliability, a friend of mine has two of them that are 3 years, never touched nor cleaned, working flawlessly; this is one case out of many so should be taken with a grain of salt.
That being said, sump flow is subjective and if you want to get all 400gph rushing through there with some power to spare I'd say something like a Sicce 3.0 would be perfect. You can always add a gate valve to restrict the flow, and a few more for future intergrations.