In the older cards you could not run crossfire with 5000 series cards with 6000series cards. So if I get a 7970 card to play battlefield would I be able to crossfire it with a 6970 or should I buy two 6970'3 since two of them cost the same as a 7970 or about the same. 7970 on sale right now for 339.99 and 7970 is 620.00... what to do what to do?????