M17x R4 Replacement Graphics Card

I'm in the market for a new graphics card for my M17x R4 as the 7970m that came with it has died and I don't wish to play games trying to reflow it. Were the issues with the 7970m production process ever corrected or should I switch to an nVidia card? If so, what nVidia card would be the best for this laptop? I assume that I only have a few options (680m-790m?). I'm not looking to spend any more than about $400 on this.

Thanks,
Eddie

M17x R4 Replacement Graphics Card