Just a general comment on your config. Is your PSU 735W? You may want to use a 1000-1200 W PSU if you want to add 6 GPUs to your rig. I am running 6 570's and mining Sumokoin (Cryptonight algorithm). My rig needs around 700 W on the wall. I use Crossair 1000W PSU.

Note that Ethereum mining will need slightly higher wattage. Also, dual mining will need even higher wattage.  So you may want to consider these factors as well.