This is what I always suggest people when they ask for a budget video card.
I always pick the 6850. In the future you will be tempted to get another 6850 because the scaling is really amazing. And imagine one card uses only one 6-pin connector has wonderfully low power consumption. Its not far away from a 5770's power consumption but gives very good frame rates at the same time.
Link to the crossfire/single card results of a 6850 with Crysis @ 2560x1600 4xAA
6950 is one of the best bang for the buck since it can be unlocked to a 6970 without paying much but the question here is that are you willing to wait long and then get one. Its worth it but people like me have a hard time when in budget situations. Probably if I keep it waiting longer I would spend some money from my savings.