Should be an easy enough answer for you guys

clutchc

Titan
Ambassador
+1^
But keep in mind, the x4 slot will drag down your 2nd graphic card that is in the X16 slot. I recommend avoiding anything other than X8 X8 or faster for SLI or Xfire. I speak from experience using x16 x4. Framerates will not increase with a 2nd card in the x4 slot. In fact, some games will show a lower framerate than with just the single card.