I think we need some clarification of terms. "Zoom" does not mean the same thing as "telephoto" - bwana's picture has several zoom lenses, including a 16-35, which could be considered a wide angle lens, even zoomed all the way in. Zoom only means you have multiple focal lengths in a single lens.
Also, the zoom factor, i.e. a 4x zoom or 20x zoom, does not say much about the focal length. A 70-200mm lens is a mere 2.8x zoom. By contrast, Canon's 15-85mm is a 5.6x zoom, despite being wider zoomed all the way in than the 70-200mm is zoomed all the way out.
So what you're really looking for is a telephoto lens, possibly with zoom capabilities. You don't say what the guy at the shop was showing you - I'm not aware of DSLR lenses that have a 20x zoom factor. The best I know of is the Nikon 18-300mm (16x zoom) which was only announced recently and is not available for sale yet. Until recently, Tamron's 18-270mm (15x) was the highest zoom factor out there.
Another thing you should consider is that, having zoom capability, is (with a few exceptions) a trade off. If you want good reach for far away animals, you will almost certainly get better results cropping pictures taken with the 70-200mm f/4 L USM than you would from just using a 17-270mm Tammy.
The Canon 70-300mm IS USM is a decent compromise between the two extremes.