hi GFX experts, I was just wondering whether it is possible to crossfire one 512MB 4870 and one 1GB 4870? I have the 512MB 4870 at the moment and I plan to crossfire it with another card in the future. With the enticing 1GB 4870 out now, I am not really sure how to make the right decision. What will be performance be like? If i mix two cards with different