It's certainly going to be overkill. you only really want 3-5x system volume going through your sump every hour (which is usually about the nominal volume of your DT give or take), so you're really looking int he realm of 500 ish GPH at the top end.
You really want to be using powerheads or a closed loop to handle the flow your corals need in the DT. For a return pump, mag drives are certainly great, but I find the eheims to be much quieter. I used to use a mag5, now use an eheim 1260, and it's night and day.