Recommend a motherboard

First off thank you for any time you take to help me   It is very appreciated.

TLDR:
opinions on what to buy for strictly gaming pc motherboard with the following criteria:

- i5 Ivy bridge CPU
- Fastest GPU available for $300 or so
- option to use multi-gpu later
- will be using onboard sound most likely
- will be using a full ATX case(CM storm trooper) so size isnt an issue
- Would like to keep it around $200 or less $250ish max if there is a significant gain



This will be my second computer build from scratch, first one was 5 years ago and it is starting to show it's age so its time to build a new monster  


I use my computer for 2 things, browsing and gaming, and I mainly want my new build to be able to play ArmA III as well as possible. ArmA is a very CPU intensive game so I am going with the best I5 chip Ivy Bridge.

I have not yet picked a GPU, I tend to like Nvidia but I am not a huge fan boy and will buy ATI if its the better card.

It's not planned right away but I would like the option to go SLI/Crossfire as needed in the future, so take that into consideration, also will be using onboard sound if possible, I am not an audiophile and have never had any complaints from on board sound in the past.