Well, I suppose that if your tank will be very lightly stocked, maybe you don't have to have a filtration level of 10 x the volume of your tank. But I personally would get 10 x the volume of my tank, even if my tank were very lightly stocked. It's not just the biological filtration that counts. You also need a good water movement in your tank to distribute heat evenly and to prevent any stagnant water.
I've been told by Gunnie, that when it comes to canister filters, 5 x the vol. of your tank is enough (due to the larger filter media capacity of a
canister filter). But I always say, and will continue saying, that: Over-filtration is always better than under-filtration. I wouldn't hesitate to use 10 x the vol. of my tank per hour even with a canister filter.