Originally posted by Michael Barkowski The 18-55 is pretty sharp for your wide angle (20-24mm) range. I'm very happy with photos from the Pentax 50-200mm DA
I disagree with you on these two lenses. I find the 18-55 to be at it's worst at the wide end (though I note you left out the 18-19mm, where I find the lens pretty ugly). I also sold off my 50-200 for a Sigma 70-300 (non-APO), and then the APO version, both of which outperfom the 50-200, especially getting up near the 200mm mark, as you might expect. The 18-55 is good for a kit lens, and a very useful range, but it's still just a kit lens.
I think Ash had some good lenses choices there, and as Michael Barkowski pointed out, it's really dependant on your needs. One thing to note though, is that even if you don't need the f/2.8 of a fast zoom, that zoom will almost always outperform a slower lens, say a f/4-5.6, especially at f/4-8.