Greetings. GDDR3 doesn't exist anymore. Where did you see it ?
I have no idea what your currency is and therefore don't understand your budget. It looks like it coeesponds to 766€, but with the same amount of money you can buy very different things in different countries.
The HD 7970 GHz is the best card for you. It's the most powerful single-GPU card from AMD. You will be able to run any current and future games at ultra settings at 70-80 fps at your resolution. So very future-proof.