I would go with the 6870 as long as the gtx 560 is not the ti version...but as far as compatibility goes you are fine that motheboard will support that video card no problem the only thing you should think about is if your psu has enough wattage for the new gpu
Thanks. But can you tell me the cheapest price for a gtx 560Ti. And yeah ..... I have a cooler master 650W PSU.