Ok i think i have found the sweet spot about power consumption and h/s for my 6x RX 480 REF stock BIOS, only overclocking/undervolting adjust :
405-420 H/s and 690-700W at the wall, maybe more if Mr Claymore can go up the hashes again with the miner

Cheers.
Can you post some details around how you achieved this? I can get the wattage but I get 320h/s in return.