Many that bites I do feel for ya ..
Search for 12-24 , 10 -20 , Wide angle lens lots of 12-24 shots. Also search on flickr. I have the 12-14 almost bought the 10-20. I like the 12-24 and at times yes there can be some distortion but overall I would not trade it. (well actually I did sell it , but I bought another one soon after
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As for generic telezoom I have the Tamron 18-250 and find it very aceptable. I believe the Pentax is pretty similar perhaps better coating ? Would do well with either.
Infrared - best is a converted camera. I think there may be one left in the markeyplace (Frak is selling them). Besides that a Hoya R72 filter - the K10D is ok, but earlier models are better (K100D, istD and the kit lens (18-55) is a good lens to use for infrared.