Go to
www.kernel.org and use the latest stable version... which I believe is 2.6.16.9 (hmmm... shouldn't that be 2.6.16-9?)... though there is nothing wrong with the prepatch and snapshot kernels, if you've never done this before you want the stable one.
You are not losing any real functionality with the 2.4 kernels (2.4.32) since changes to the 2.6 tree get ported to the 2.4 in short order. If you want to improve functionality and ease-of-maintenance, you should change to a more up to date distro altogether
I'm curious... how did you get hold of RH9 and why did you choose it out of all the possibilities?