I'm in a similar situation, kinda.
I posted on here a while back about the qualities of the XSi compared to the K200D. If you go back a few pages, you'll find it. The thread was closed for further comments, but it might help you out.
I used to shoot with an older Rebel and have used an old manual Pentax for black and white.
I ended up buying the K200D because it felt a lot better in my hands, and I liked the cleaner layout (although I'd rather have an ISO button than a RAW), and I like the use of AA batteries.
But...
I'm an indecisive sob.
The camera arrived a few days ago, but I haven't even shot with it because I've been second guessing my decision based on the performance of the autofocus.
I have about a week or so left where I can return the camera for a refund.
I'm just using this for a hobby, but I'm interested in taking sports pictures, specifically high school sports and professional wrestling.
I have scoured the Internet and have been unable to find a lot of examples of good action shots taken by the K200D. I've found a lot taken by the XSi. I'm sure some of this has to do with the proliferation of the XSi, but still.
From the samples I've seen, the ISO quality isn't a huge factor. I've seen some pretty good shots from the K200D using 1600.
Of course, I guess I could always use manual focus. Although I read on some places that you can't visually tell if the image is focused when using manual? Is this right? And I also read that by using a flash, the autofocus will improve significantly as the flash may emit an infrared beam of some sort to help with focus. Is this right?
As you can tell, even though I've used SLRs, I'm still kinda ignorant.
Hopefully, someone with some brains will come along and add something useful.