With microcenter if you buy an i5-2500K you get $50 off on a Z77 motherboard. My advice is to get a $100 board for $50 like this one http://www.microcenter.com/single_product_results.phtml?product_id=0388327
And that would be $230 total before tax, in store pickup only.
Then get yourself 8GB of RAM ($45)
And a 500GB HDD ($60)
This is what I would do if I lived near a MC. It might push you over your budget though so you could go with a cheaper GPU. I would definately go for the i5 and board for $230 though because people like me that live nowhere near a MC have to pay $230 for just the i5!!!