Amgclk65,
Thanks for updating the post!  You made me re-visit my 6 x 270 setup and realize that I was pushing WAY too hard for those final few Khash.  Running slightly lower hash rate (5-8%) and consuming significantly less power (20-30%) IS THE WAY TO GO.

I'm now running 900/1080 intensity18, powertun -18%, with an expectedly lower hashrate (380 kh/s avg), but surprisingly close work units per minute (350wu/m) to what you're getting.

The rig hasn't been running long enough for exact results, but I'll update in a day or two with additional figures. Initial power consumption has been around 690 Watts (linux usb flash drive build, no HDD, no optical drive, no case fans).

If testing at 1.000V @ 900/1080 goes well I'll push for under 1.0.  Last time testing 1.000 volts I suspect my core clock and memory clocks were too high causing instability. 

If anyone cares I'm running Asus D2C R9 270's.

Cheers,
- VR