Simple, probably stupidly easy question here. I've been seeing an XFX 6870 on sale on Newegg for $130 recently. I've got a (I think) Sapphire 5850 in my current rig... it probably wouldn't be worth the money to upgrade between the two? I should preface this with the fact that I seem to be unable to OC my 5850 in even the most slight way.
No that is not worth the upgrade, you should be looking at a HD6950 or 560Ti for a decent performance bump, assuming your system is up to it. Power supply is able to run new card and CPU powerful enough.