I'd second the Fluval 406 recommendation. Plenty of flow in my 75g. I've actually been wanting to do a similar native tank. I quickly decided against the SMB because of their adult size. I would recommend some sunfish (blue gill, greens, pumpkinseed, etc) instead. They stay smaller and you could do a few in a tank that size.
Unfortunately - or fortunately - every time I go out looking for sunfish I end up with bass or cats. Never thought I'd have this problem.