[disco_owner]

I was gonna chime in with the Sigma 120-300 f/2.8 but it doesn't come in K mount

that would have been an awesome lens and more useable than a Prime 300 2.8. Unfortunately as you stated it doesnot come in K-Mount as yet. Sigma 120-300 would have been my first choice.

[crf529]

But the 300mm F2.8 is a completely different sort of beast. It's professional grade glass that costs two-and-a-half grand and weighs two-and-half kilos. You'll be using it on a tripod (or perhaps a monopod) and you'll look a complete poseur.

I use mine all the time on a gripped K20D without a monopod? The only time I use a monopod is when shooting surfing...