[Monobod]

I have found that the Sigma 17-70 f/2.8 - 4.5 zoom give excellent results on my K-5. But the 2.8 disappears as soon one moves the zoom ring!
Also the Sigma EX 10-20 f/4-5.6 is a stunning lens. Although it is not available new any more the Sigma 100-300 f/4 performs very well on the K-5 even with the 1.4x tc. If you can find any of these in mint condition s/h you will not be disappointed.

Another lens worth looking out for s/h is the 70-210 f/4 one touch manual focus zoom. If you use 'catch in focus' you can hold down the shutter release and twist the zoom/focus ring. As soon as focus is confirmed the shutter fires. This is a very sharp lens with excellent contrast.

PS - I might be listed as a junior member, but I have been involved with photography for over 50 years! smile.