@csa,
Sorry for taking the thread a bit off the direction you intended. It did annoy me to see a valuable member and a great photographer just be rudely attacked for no reason.
And Greg (northcoastgreg) is too humble to direct people to his site, where he reviews a few of the lenses you would probably consider, which would be in or very close to your budget:
http://www.northcoastphotographer.net/blog/index.html
Look for these:
. DA 15mm f4 Limited (used older SMC version can be found for around 450 here at our Marketplace forums)
. FA 20-35mm f4 (around 300-400 used, no longer made)
. DA 17-70mm (can be found used for just over 300 dollars at keh.com with 6-month warranty)
. DA 16-45mm (can be found used for around 200ish, no longer available new)
. DA 12-24mm (probably out of your budget, but still worth checking out...)
Look in the Pentax reviews in this forum as well, as someone already pointed out. I find, however, that it is useful to see the lens in actual use - without lots of post processing that make the actual lens output almost irrecognizable - instead of just reading about it. So do a search on flickr for the lenses you are considering and you'll see all sorts of people who use them - some without any post processing at all.
As for me, since I have a much lower budget than most, I went with a Tokina 19-35mm f/3.5-4.5. It's actually pretty decent, especially considering the price. It works for me, but I have no professional aspirations in the near future...
Good luck in your search!