Originally posted by trishytee I then read the reviews on all three and got totally bamboozled! In fact it seemed that the Kx was just as good as the K20 and not that different to the K7.
I don't get that, as good in what way? The K20D and K-x have totally different strengths.
If you want faster AF in low light, AA batteries, small size, more frames per second and one stop higher ISO performance, go for the K-x. The K20D is a more professional style body, with buttons instead of menus, WR construction, more resolution (for cropping and larger prints), larger size (for better balance with larger lenses and external flash), a grip, more control over settings (e.g. User and TAV Modes), a larger viewfinder. Tests show the K-x has greater dynamic range, but I haven't noticed anything in actual use. I do have a slight preference for the K20D image quality at low ISO, but I tend to use the K20 and K-x for different purposes. They really are very different beasts.
The K-7 low-light focussing equals the K-x except it has an AF-assist beam (nice feature) and focusses more accurately than K-x or K20 in Tungsten light (great feature). It shoots frames a bit faster than the K-x. It's a bit smaller than the K20D but otherwise is very similar.
Trishytee, you sometimes shoot weddings don't you? Personally I think the K-7 is the one to get as a main camera for pro use and learn to work around the ISO disadvantage. It's just more camera than the K-x and addresses the main weaknesses of the otherwise superb K20D.