After flashing the BIOSes I've got some new numbers:
ETH - Total Speed: 125.836 Mh/s, Total Shares: 1667, Rejected: 1, Time: 08:34
ETH: GPU0 24.887 Mh/s, GPU1 25.462 Mh/s, GPU2 25.494 Mh/s, GPU3 24.638 Mh/s, GPU4 25.355 Mh/sThis pulls not more than 680 Watt at the wall

Flashed the cards with tutorials from
http://1stminingrig.com/category/tutorials/Undervolted -50mV using TriXX.