A lot of thrifty advice, probably a sign of our economic times. Like the others say, you probably don't "need" a different rod, but a "need" is relative, isn't it.

I say there's nothing wrong with having multiple rods, if you can find a reason to buy one(and can justify the cost). While a 5 wt works fine with dries, lighter is better if you're going for spooky fish or clear water. If I had a rod strictly for dry files it would be a 2 or 3 wt. But on a typical day I fish both wet and dry and find a 4 wt to be the best of both worlds.