Umm, I would go with a 6870 if you don't like to deal with rebates. If you do, go with a 560 Ti for sure. Don't feel remorse from getting a 6870 though, they perform almost as well as a 560 Ti. But then again, a 560 can overclock WAY high! Like, 570 levels!
Motherboard : $125-Gigabyte GA Z68MA.
The only con of this board is its mATX. Otherwise it supports SLI & Crossfire at 8x/8x. And other features. You can select any other board in this price range if you don't like this one.
If you can stretch your budget by a little more, here's another Gigabyte GA-Z68x or you can drop down to the mother board you selected.