not really sure what MH to expect my 2 370 do 27 to 37 mh or so with out the 280 , the 280 is for every day use so i don't use it much to mine with.
I also have a 7870 i may fire back up in a few days that's WCed .
I am gonna set it all up in a open frame once the frame comes and might buy eth OS to see how well that does sense i don't care much for win 7 .
I've been using EthOS on two rigs for nearly a year now and it's great - I recommend it. I tried using Win7 and Claymore for a while because I wanted to easily swap to mining XMR and ZEC but now EthOS has that covered too.
Using SGMiner-GM in EthOS to mine ETH I get a better hash-rate than Claymore but with no fee and similar (actually slightly lower) power consumption. I think that Mining ZEC and XMR I would get better hashrates with the Claymore miner (which EthOS has for ZEC but not XMR) but with the ETH price where it is I'll keep mining it until it goes POS or if it's price dumps too much.
If I had the Linux skills to just do it all myself I would, but EthOS is a great way to have a really stable solid Linux rig without having to learn a whole lot of Linux. It's pretty easy to set up and use if you have ever used Linux even a little.