I know that radeonhd does cause some issues with KDE desktop effects, but according to Radeon - openSUSE, the cards above X1900 should be using radeonhd.
Instead of either of these, should I try to use the ATI driver fglrx? It seems from my gleaning of forum posts that these have some problems, but I am having some desktop effect issues that maybe would be addressed with that driver.
I don’t remember exactly how I did it, as it was about a month ago, but I’m pretty sure that I was able to switch from a non-working fglrx back to radeon (I have an x800) by replacing the xorg.conf generated by fglrx with a pre-install backup copy I made. I then got rid of it by totally removing it in YaST, and then made extra-sure it was gone by running:
rpm -e $(rpm -qa | grep fglrx)
Again, that’s off of memory… so I’ve probably forgotten something important. Though I don’t remember getting rid of fglrx to be a huge hassle, so it can’t have been much more complicated than that.
In regards to your question about why radeonhd isn’t loading, did you check any of your xorg logs for error messages? They’re in /var/log and usually have lots of useful information if something doesn’t load properly. Xorg.0.log would be the first one to check for any problems.