Depends on what you can afford. The 6870 or 560 will do quite well with most titles at 1080p. The 560Ti is about 10% faster and will provide noticeably better performance in the small selection of really graphically demanding titles. If you plan on playing a lot of Witcher 2, Battlefield 3, Crysis, Crysis 2 or Metro 2033 you may want to invest the extra money in either a 560Ti or 6950 1GB. If not, you can get away with a 6870 or 560 non Ti, though you may have to look at an upgrade slightly sooner down the road. It will depend on when the new console generation hits, or if the developers get tired of the XBox 360's limitations and start focusing more on pushing PC hardware.