Other people may have better ways of doing this, but I initially got RivaTuner v2.22 just for the capability to monitor the cards, which is how I learned that they were running underclocked and using it's other features to manually adjust all the settings. I knew something was wrong because the PC would frequently freeze up especially when trying to play games, which led me to looking for a way to monitor system performance.

As far as the current operating specs of your cards, you're probably going to have to look on the box, builder's website, or search for the part's specs on the web to determine what it should be running at. Keep in mind that different manufacturers may tweak the specs for their card, so not all 4870X2s may be the same. I'm running dual 3870X2s, so you should also be in the 825MHz ballpark.

EDIT: Played with this after getting home. The power settings changes haven't made any discernable difference in regards to the performance of my cards (yeah, I updated both through the GUI and regedit), they still want to run underclocked without using RivaTuner. Updated to latest 9.6 ATI drivers and CCC (dated 6/15/09) which I hadn't seen yet in case latest drivers would maybe correct the issue, but no luck there either. No harm done I guess, since I already stated that I'm working fine with RivaTuner.