According to this review an overclocked 570 beats an overclocked 6970 and is also slightly quieter so if it were me I would get a 570. Having said that being able to unlock a 6950 to a 6970 is very tempting. I do prefer nvidia so i'm slightly bias tho.
Edit: I hear SSD's are a great upgrade so I would get one if I had the cash
Also, what is the Novatrise code?