I have a Pentax *ist - I want to supplement the kit 18-55 lens with a longer zoom. I'm considering the DA-50-200/4-5.6 by Pentax. My needs are fairly moderate - mostly snapshots. Is there any other consumer zooms I should consider? Other manufacturers? My budget is quite modest - so I cannot go after the really good glass. Any help would be greatly appreciated. TIA, Pinaki.