I just found a shop that is clearing out old stock, I have not built a mining system yet but have the opportunity to pick up a number of these cards at $550 a pop( potentially less if I buy multiples). Is this a decent price for setting up my first mining rig? Or should I stay away from these older cards and get something like the newer 290x's?

edit: its the Gigabyte GV-R799D5-6GD-B 6G  Model