A 200mm lens is pretty long on an APS-C DSLR, equivalent in length to a 300mm lens on a traditional 35mm (or "full format" DSLR) camera. Of course, you may still find that length limiting for some purposes, but it's more than adequate for most genres of photography. And new or used, the 55-200mm zoom (with or without VR image stabilization) is a cheap lens that will let you explore your direction in photography without a major financial outlay.

Perhaps the most important thing when buying photographic equipment is knowing what you really need. Lenses, especially, can become really expensive in a hurry. By exploring the cheap option now, you will be in a better position to decide, when the time comes, whether you need, say, a good, fast, long lens (zoom or prime), or something with the ultimate in versatility (like, say, the 18-200mm zoom). The relatively low price of the 55-200mm will give you the full range of focal lengths, and you can tell by the kinds of pictures you find yourself taking (or still wishing you could take) what your next step should be. If all or most of your pictures are at longer focal lengths, then a faster 70- or 80-200mm zoom might be the ticket. If you find that you're working consistently between 55 and 100mm, then you might find that a shorter zoom or an 85mm prime lens is really what you need. Or you may find that having the "dual kit" is perfectly adequate for your needs.

If the 55-200mm doesn't do the trick for you, you can sell it for nearly what you paid for it. If you splurge on something that doesn't scratch your immediate itch (wanting a longer reach), you may find yourself with something you'll take a significant loss on when you change your mind. Don't worry about what's "right"; take the time to figure out what's right for you. When you're ready to jump into the deep end, you'll know.