You should probably look around a little bit at what the different DSLR models offer. They'll all be compatible with your lenses. You can always pick up a used version of most of the cameras to fit your budget.
I had a K10d. I liked the camera, but its lowlight abilities were lacking. In all honesty, I didn't think they lacked much until the K5 came out and I saw what a real lowlight capable camera could produce. I still use the K10d because in normal light situations, I still find it adequate, and I actually like it ergonomically a bit better. It may not have all the bells and whistles, but I was used to it and there are certain things I just like better... Specifically, I like the size of the camera. It felt much better in my hands than my K5 does. The grip on the K5 helps, but I hate that I had to spend an extra $200 to get the right fit. I also liked the mode dial better on the K10d. That is a minor quibble. I definitely love my K5 and it does take 95% of my shots. The K10d is mostly there for odd lens shooting with a second body saving a bit of work.
If you are looking to save some money but perhaps still make an upgrade, I'd consider the K200 and the K20. The K200 was essentially the same as the K10d without the weather sealing (it was an entry level). The K20d was the K10d's replacement. You get a few more MP and a bit better low-light performance. I think it uses the same batteries and is the same size. The next steps go towards the K7, Kx, and Kr. The Kx and Kr are the successors to the K200d (I don't remember what came first), and the K7 is the predecessor for the K5. Others have given comments on those cameras from their first hand experience, which is better than my zero hand experience