MSI Radeon HD 6970 Lightning, how good is old lightning and can it compete with GTX580?

Hi everyone Around a year ago I found MSI Radeon HD 6970 Lightning - this is top of the line single chip one of the most out-of-box overclocked version of HD 6970 (second generation of AMD DX11 GPUs) which has massive VRM. It's time to service it, test it, overclock (and overvolt) and see how good is old Lightning card and can it compete with absolute monster EVGA GTX 580 Classified Ultra 3G and it's overclocked version