I have 3 480's setup in Crossfire on my Rampage IV Extreme. The XFX card draws more wattage (And by default has a higher clock then the rest of the cards). After running 3dmark (First thing i did with the 3 card together) I lost my audio ports. Reading elsewhere audio would be the first thing affected.
Rampages IV have had reported audio issues in the past in-which maybe the cards triggered, or the cards did itself by pulling a crazy amount of wattage.
Later ill be removing one card when i get home hoping my audio port comes back, If not submitting RMA on the XFX card since it was the last one to be installed before losing audio.