R9 Nano in X51 r2

I want to put a new graphics card in my R2 to upgrade from the current 760Ti, I understand new GTX cards are coming but that looks like a long way in the future so I need to do something now. I have looked at the GTX 970 but that does not look like a big advantage from my current card. Maybe only 30% or 40% faster but the r9 nano looks like it could be 60 or 70% faster so would prefer that option but I don’t want to waste cash if it will not work.

Looking on the forum one person said he had used the card with no issues, but I can contact him to confirm. But looking on the R2 fitment chat I see a ?

I also need to understand if I need anything additional like a different power cable or adapter?

if anyone has used the R9 nano which one?, or if i need the GTX 970 which one fits without modification

I do have the 330w power supply but need some guidance

Any help would be much appreciated