G'day and welcome to the forum.
"Basic hobby shooting" consists of what for you?
Any of the above cameras should do the job fine, it will rather be the lenses you choose that will determine their suitability to your chosen style of shooting.
None of the cameras would disappoint, bearing in mind the K20D is quite a refined model with advanced features for when you want to take your photography more seriously.
Nevertheless, the K-x performs excellently and can boast of much of the features that leaves its rival models for dead.
Also check out the forum's reviews of these cameras in the Camera review database in the Reviews section on the above tabs.
Hope this helps.