We have just got the normal 6.5 inch stainless ones for their food, with an 8.5 inch for their water. We got two stands last year at Crufts which are 6 inches high - the smaller bowls fit into the top, and the larger bowl fits into the bottom when you flip it over! This means the dogs eat without having to lean right down to the floor and when they drink their ears don't dangle in so much !! They don't need both at once, since one large water bowl suffices when they have finished their food.
We think they are much better than having the bowls on the floor - they stay where you put them for one thing !!