Something that might be a bit more helpful: it depends on how much space you have, what you want to keep and what kind of look you want.
24" is the max height I like since it's harder to light tanks that are deeper (not to mention reach all the way to clean), but some people go as deep as 30"
48" is the minimum width for keeping the smallest tangs
24" is the _minimum_ depth IMO for good aquascaping...30" is even better. I wish I had at least that much.