The Antec Neo ECO 520 is a very good power supply and it's made by seasonic, so you can buy that one.
But anything from Seasonic, Corsair or Antec its a good choice.
Would this one be a good choice? http://www.pccasegear.com/index.php?main_page=product_info&cPath=15_535&products_id=21569
and the reason i needed to changed the power supply is because the Antec Neo ECO is not on the site anymore.
i will be running a Sapphire Radeon HD7850 2GB OC V2 and Intel Core i5 3570K.