I fixed my problems if anyone is having similar issues with low hashrates on 7950s when mining X11 coins.  I couldn't get any of my 7950s above ~650kh/s running Xubuntu 12.10.

I had to uninstall every trace of Catalyst drivers and then install the latest Catalyst Drivers from AMD (14.4 at time of this post).  I was running much older 12.9 Catalyst.  I then had to compile sph-sgminer from source which is no small feat tracking down all the damn dependencies.  

At any rate, that fixed it.  I'm now getting 1.6Mh/s+ from each 7950 without hardly any tweaking.