I got a great deal on a Canon 30D, then upgraded to a 7D recently.

Ash is a little off, sure a 18-55 has a 3x range. On a crop camera (aka any affordable DSLR) there is a 1.6 factor. To calculate the zoom you divide by 35 mm (relative to the old film "standard") then multiple by 1.6.

18/35 * 1.6 = 0.82
55/35 * 1.6 = 2.5

So your effective zoom range is 0.8 - 2.5x

Knowing WHAT you want to shoot is the biggest determinate. I like shooting action shots, so I bought a 70-200mm and the fastest canon under $5k. This setup has a 3x-9x zoom range.

If you are not worried about low light or fast speed or snappy response or very wide angle, etc . I would consider a PnS with full manual capability.

Now that I mention that, you can start experimenting with your camera to figure out where it is lacking for your desires. Know what effect changing your iso setting has, then playing with Tv and Av modes (most people use Av or full manual). These settings were not easily accessible on my Canon SD880.