I've shot with the K10, K-M, K7, and K-X.
If I really, really, really had to stick with one, I'd pick the K-X because, among other things, I shoot more indoors than outdoors. There's no comparison in image quality at low light, high ISO. Not close.
I get shots I'd never get otherwise and that's the key.
Nor do I like the K-M white balance or focusing ability in yellowish light, even outdoors early AM and late PM.
I won't go on. Pick the K-X and save for lenses. Check the used market. Anything that allows you to keep the K-X.
But if you insist on the K-M (K2000), I'm more than willing to part with mine
And if you're wondering, I'm dumping the K10 and K-M, keeping the K7 for (generally) outdoors and K-X for (generally) indoors. I know, I'm a lucky guy. Spending retirement money early.