for resolutions upto 1080p you cannot get any better card than the 6870 in that price range. you could x-fire later, and would give you a decent life.
Motherboard only supports one PCI Express card (H61 Board), so that isn't an option.
But I am pretty much settled on either a 6850 or 6870. Are the Sapphire cards of decent quality?
They looked cheaper in case and cooling compared to HIS cards, but they seem to get better reviews.