I would suggest one of these at your budget:
http://www.newegg.com/Product/Product.aspx?Item=N82E16834230174 quad core i7, gtx 560M, although is recertified and 1600x900 res
http://www.logicbuy.com/deals/hp-envy-17-laptop/19986.aspx dual core i5, radeon HD 6850, 1920x1080 resolution.
im not sure whether or not these would be able to run sc2 on highest with 30+ fps throughout, but these, for the most part, offer the best price/performance at this budget.
you won't see many benefits from the quad core i7 if your primary usage is sc2.
EDIT: it's also fairly difficult to find a low capacity hard drive in a $1000 laptop.