2x 2GB sticks is the way to go for 4GB, always. You need a 64-bit OS to get "real" use out of 4GB. So if you haven't bought a OS yet, I would probably grab a 64-bit one. If not, not a huge deal, 2GB is still plenty from my experience except for one game that had a minor memory leak.
For motherboard, my choice would be:
Gigabyte GA-P35-DS3L
Grab bang for your buck board, will OC well, and should be extremely stable. I'm a HUGE Gigabyte fan after my own experience for the previous motherboard in this price slot based on the P965 (chipset before the P35) chip. It has taken my E6300 from 1.86Ghz default clock to 3.15Ghz OC'd. Not a single stability issue either! So I would certainly expect the same great experience from this board.