Based on my extensive reading you will want a minimum flow of water that is 10x the tanks capacity. In your case that would be 550gal/hr minimum. Two powerheads that are rated for 275 gal
/hr (aprox) would do the trick. Your filtrationwill add to that but that is a good thing. Some aquarists use 20x or30x per hour.
I'm probably on the high end right now with my 46gal tank. I have a 200gal/hr powerhead and a 300gal/hr powerhead. I'm also running a 175gal/hr canister and a AC300 with an unknown output.
So far I don't seem to have any problems with the diverse currents in my tank.