I have read that as long as the fish aren't pinned up against the glass or substrate blowing around then it isn't too much flow.
Though it's all about relativity, utilization, and position.
In my 55g I have:
1 x koralia 750gph
1 x koralia 240gph
1 x 300gph return pump (split into two)
1 x MJ 500gph (replacing soon with koralia 750)
So that will be total 2040gph once I replace it. I still probably won't feel like it is enough.
In my 10g I have
2 x koralia 240gph
1 x 100gph return pump
That's 580 gph
in a 10g and I don't know how that will fare yet.. haven't added any corals. My fish love the currents though.