So I have been running mine wide open at 750 MHz (the max you can set), is it seems to take it just fine.

Here's power consumption running at 750 MHz.  Note that there are peaks as high as 485 Watts, so keep that in mind if you plan to run several of these from a single PSU.  The baseline consumption running maxed out is 350 Watts.

http://www.cstone.net/~dk/z9_750_10.PNG

After 5 hours 20 minutes, average KSol/S is 16.39 and 0 HW errors:

http://www.cstone.net/~dk/z9_750_11.PNG

And things are looking great pool side as well:

http://www.cstone.net/~dk/z9_750_12.PNG

http://www.cstone.net/~dk/z9_750_13.PNG

From the above graph, you can see where I went from a 650 to a 750 OC setting.

Wish I had about a dozen of these last fall!