that does sound low, but sounds about right for a single card. Make sure you have crossfire enabled . Also check your bridge to make sure it is well seated. Your two 5770s will not outperform a 5870, so don't expect the same score.
One major problem the windows program has is that it will not kick your video cards out of power saving mode. So instead of having your normal core and memory clock settings that you normally get in a video game, you are running at 1/4 the normal clock settings.
Forget the index, it will not work on any of ATI's energy saving cards.