Karn:
"Anyway, I've pretty much made my mind up, ... a K20D + Sigma 17-70 + Tamron 70 - 300 + bag/tripod/uv-lenses etc. is well fitted. " ...may I be so presumptuous to offer an alternative opinion? IMHO: What you are doing is setting yourself up for disappointment and a bad case of LBA (lens buying addiction). The K20D is so good that the subtle flaws of each lens will be highlighted. Initially, you will tell yourself that you are pleased, but as your flaw correcting work arounds fail, doubt will set in. It begins with the wish that the image could be just a little sharper (like Daniel Tong's birds, or Ben's models, or...). You'll tell yourself not to worry... you can use post processing to save it. Nah... that didn't work. And so on... until you cave and get a "Limited" lens.
Want in on a secret? (Pssst... it's all in the glass.) Camera bodies are obsolete the day they hit the market. Good glass, like my M42 1:1.8 55 (1962), is forever.
You picked the K20D because you feel it is the best fit for your purposes. Don't think for a minute you can quench that desire for the 'best' by doing a glass 'cheap out.' A bare bones K110D paired with a DA 40 Ltd or FA 31 Ltd (and good pho-tog's eye) will beat your bag of goodies almost every time.
Anyway... my .02 cent$ is to pair the K20D with a single lens. I suggest the DA 40 Limited which can be acquired for about $275. The DA 40 Ltd is an optical marvel and an expression of technology at its best. Work the lens hard. Learn it to death. Trust me... your results will be dazzling from day one (as opposed to "good").
While you may want it all now, do you really need it now? If you take my suggestion, you will save a ton of money and learn a lot. Over time, as better lens choices emerge, you eye and use habits will tell you when to consider adding to your lens portfolio. LP-A (learn, plan, then act...) beats LBA, every time.
Good luck &
shooting...