This is a very good power supply, and should be able to handle 2 270X's, although the peak load will be quite high. TDP of each 270X is close to 180W at max load, leaving you with peak theoretical load of entire system (CPU+drives+MBO+2x270X) of close to 500W. It is unlikely that you will ever reach those figures in real life, though. You'd have to OC your CPU, load it to 100% and load both graphics cards to 100% as well. In practice this is highly unlikely, especially over long periods of time.
Frankly, I've never been a fan of SLI or Crossfire. I'd rather sell this 270X when it gets underpowered and just get 1x 290 or 290X.