Originally posted by redpit You shouldn't compare the bigma to the DA 560 IMHO. If you need a supertele with great IQ even from 5.6 then the DA 560 is the way to go (the Sigma 500/4.5 being the only other option to buy new - if its still available somewhere).
If you want Pentax, the 560 is the only chance - currently. I decided against a new 560 or a used Sigma 4.5/500. From other brands you have a lot more used/new options that are better suited. I like my K1 and don't want a second system, but for long tele work there is no way around it for me. I especially like in lens shake reduction - if you want to work without a tripod. Yes, Pentax can nail AF, yes in body SR works, but for the life can be easier and not more expensive.