OP, it looks like you've got a solution, but since I went from a K10 to a Kx for the exact reasons you're talking about, I'll write this post
Originally posted by rawr A brand new K-x kit deal would probably be cheaper than a DA* 16-50, and give you better low-light, better AF AND higher resolution, video etc.
Or just get a FA50 1.4 for when you need to do low-light and keep the K10D.
YYMV, but it didn't work for me :P In similarly dismal lighting, my high quality FA50 1.4 (a fantastic lens that takes gorgeous shots) on my K10d couldn't hold a candle to my decent-but-slow FA100-300 4.7 on my K-x. It wasn't the lens - it was the camera. The autofocus on the K-x is way ahead of the K10 and the ISO availability makes low light shooting a dream. There were so many times I just gave up on getting the shot with the K10 because putting the ISO above 800 made the shots unusable, but with the K-x I shoot practically in the dark.
Ahem. Okay, I'll stop raving now :P Seriously though, I went from the K10 to the K-x specifically for these 2 factors - greatly improved autofocus and fantastic high ISO shooting and it has been everything I wanted and more. Best part? The K10 fetched enough that I hardly had to shell out any money for my K-x - once I sold the two kit lenses from the K-x kit, I'd actually made money on the transition :P
This shot would have never worked for me on the K10 - FA 1-300mm zoom at f/4.7 in a dark dark coffee shop. I needed ISO 1600 to get a usable shutter speed of 1/160. On the K10 at 1600 the photo would have had bad vertical banding and lots of un-pretty noise. At 1600 the K-x isn't even trying hard :P I could have taken the shot at 3200 or 6400 and had a lovely shot, and probably would have if I'd had time to adjust the camera - but this kid runs from me when I'm taking photos
The slight grain in the background of the shot is PP because I like the texture.
.......not that I'm trying to tempt you to come to the dark side with the K-x users. Oh no. Not at all