From what I've read, you can't flash 6950 to 6970 on newer cards. That was possible only on early releases. Correct me if I'm wrong.
Anyway, this is a subjective matter because I used to game on a laptop (everything on lowest possible settings) and I'm currently on a computer from 2003. Imagine what will jump to above specified rig feel like. Even a card like 5670 would feel like a miracle to my eyes because I'm used to bad graphics.