I must agree that the K10D is an excellent camera and if you do not expect to print larger than A3, then it will do all you require. However, the K20D does have a version of liveview, very useful for macro work and it does have a low noise sensor, useful if you do indoor photography, where high ISO is required. High ISO ('film' speed) is also useful to give faster shutter speeds for telephoto lenses to reduce camera shake affecting sharpness.

If you have the cash, I would suggest you buy the K20D. You may want it later and then you will lose money heavily when trading in a K10D.

More lenses and accessories can follow later, get the best camera you can afford now.