You might add some wave like powerheads in the main tank and use this pump.
That will give you the needed flow, but not require a larger sump pump.

I'd do this personally:
If you can drill into the bottom of the tank, adding a pair of 3/4" bulkheads and hooking a large canister or an Ocean clear + foam core ought to help a lot and reduce noise/overflow issues etc.

So you have a sump/overflow + a canister on different loops.
Get the best of both.
Remember detritus is going to be pulled in the lower parts, and the finer junk up into the overflow. The drain side on the bulk head to the canister may also be used for water change drains by adding a Tee.
Simply add a soft hose to the drain, etc, where ever you want it to go, and turn it on. If you can leave the drain hose on, or hide it etc so it's not obvious, then it'll make water changes easier.

You can do the same for the fill on the canister return to fill the tank if you wish, no splash, it's at the bottom etc.
Add a Tee to that also and do the same thing, turn a pair of tees to drain and fill and turn the water main on for the fill(do not leave that on all the time etc, just when you want to refill the tank, then open the Tee to fill, when you have enough, close the Tee and the ball valve, then go turn off the water at the main shut off).

Hard to explain but very easy to do.



Regards,
Tom Barr