I will comment on the superzoom. I had a DA18-250mm for 8 years. I bought it 2nd hand and I love it. An excellent all around zoom lens, very sturdy. But it was old and I had to replace it after 8 years of hard work. I bought a DA18-270mm for replacement. In my opinion, the DA18-270mm is an improvement over the DA18-250mm for its silent and faster AF, and the (small) extra reach. The IQ is very comparable IMHO and decent.
I tried briefly the Sigma 18-250mm but it is very heavy. I carry my camera when bushwalking and I value the Pentax camera and lens system for its small size and weight.. The Sigma 18-250mm was too heavy and I was nor comfortable. The Sigma 18-300mm is slightly heavier and I did not consider it.
In summary, if you want value for money and (relatively) light weight, a DA18-250mm in good condition would be great option IMHO, as mentioned earlier. If you have more funds, the DA18-270mm is good option for new lens with warranty.
My 5 cents, hoping that it may help.
Last edited by hcc; 05-10-2018 at 10:51 PM.