Tech speaking you can't flash it to a 6970...It gets close to a 6970 but then again you can just oc the 6970 and it pawns the 6950 unlocked 6970..Anyway I know I own 2x 6950's that are unlocked and a 6970...Moving along.
Best bang for buck below 2k is a MSI R6870 Hawk, I think they go for R1900 from Take2.
If that's still to much try looking at a Nvidia GTX 550TI, they sell for between R1300 and R1500.

Or I'll sell you my Asus 6870 DirectCU for R1600 Its laying in its box waiting for a new owner