Take a look at what Gigabyte has to offer, check on New Egg and other sites for costs and specs...you should be able to find something in that price range that will do the job.
I'm building my first gaming desktop. Here's what I've got so far...
i5-2500k sandy bridge
Nvidia geforce 660
500gb hdd
8gb RAM (depending on mobo)
Cooler Master HAF 922
pretty much everything except a good motherboard. $200-$300 price range. Not looking at SLI. Needs HDMI.
Ideas?

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic