welcome and have fun, sorry i didn't see the thread earlier. what i would have told you would be "go for the k10, if on a budget, and stop worrying". basically any camera made by pentax (and frankly all the others too) after the k10 (included) is great, the k10d is also a piece of history (a game changer). in other words, the k-r is absolutely fine, stop worrying and continue shooting, you've got great gear.
shutter speed: this is a commonly misunderstood factor i feel: for sports (subject moving across your frame), the highest useful shutter speed is really the sync speed (modern dslrs means somewhere between 1/160 and 1/250, pentax is 1/180 i think), making it faster than that will help little if at all. higher shutter speeds are useful in bright light, so you can control your aperture (use a wider aperture for nice dof effects etc). to understand why that is, you'd have to learn how a focal plane shutter works, if not technically inclined, just remember the rule above and keep it in mind (it will come in handy when you're shooting rally and bump the shutter speed to 1/4000 or such, at cost of iso and dof, and see no improvement in "motion sharpness", you will know to clam down, bring iso back down, aperture back up, and start tracking the motion carefully
)
edit: hmm, let me tone that down a bit: let me replace "higher than sync speed is useless" to "is problematic at best". experiment and you will see
for the curious:
http://en.wikipedia.org/wiki/Rolling_shutter
have fun, and stop worrying about the gearfor a year or two