I just upgraded my Dell XPS 730x with a second HD 4870 X2 card.
Using 2 - Dell 27" monitors
WEI increased from 6.0 to 7.2 for both Graphics and Gaming Graphics.
What surprised me was that the Hard Drive Score increased by .4 and the Memory(RAM) increased by .3
I made no other changes.
Card was easy to install, just had to restart the computer a few times to get all the settings right. (turn off the Cross Fire) WIN 7 Pro x64 was able to recognize the card and everything works great.