5 months is crap: Two points to consider: Your Calculation is based on a constant difficulty. Look here:
http://bitcoindifficulty.com/ and make your own guess on how hight difficulty would be in 5 months.
Second: Break Even Point is not the Point when you get your hardwarecosts back. Break even poin is much earlier: When you have mined that many coins (and exchanged them) that you would have no profit and no losses AFTER Selling your used Hardware you reached the break even point. That would be after mining 25-35% of the original value of your rig. Everything you mine after that is profit as you can always sell your parts..
Your build seems fine. Perhaps use a cheaper Mainboard: For two cards: ASRock 970 Extreme3. For three cards: ASRock 970 Extreme4. And I don't know how good XFX PSUs are. Corsair or Seasonic are very good ones.
Maybe this one: Corsair Professional Series HX750 80PLUS Gold 750W or this one: Corsair Professional Series Gold AX850 850W (three GPUs)