Yea, I had five on high through this Kill-a-watt.  1718watts/5 is about 343.6watts each.  I would use both cables to be safe.  I did run two Cubes through one PSU for a bit and the PCIe power cable got much warmer than using a dedicated cable for each plug.

http://i.imgur.com/LmsYjG7.jpg?1

I'm also using the CX750M's on all Cubes.

http://i.imgur.com/MipJ8dq.jpg?1

I did have a problem with two cubes going all x's on me, had to switch out a PSU plug to another circuit.

-herener