My boyfriend used to have an Alienware, I believe it cost a little more than �1200 new but you could get a reconditioned one on Ebay. He recently sold his, pristine condition, for only �750.
I'd say the best for gaming are the Dell XPS range laptops. I think you may be able to get 2nd hand ones within your budget on eBay, and with factory restore, it should run pretty sweet. They have a good enough processor for your design work too!