Huhhh?!?!
Whats the point of make him buy a GTX960 if he already have a 7970??? The 7970 is as fast (if not faster) than the GTX960. You just make it spend 200$ for nothing!!!
So personnally, if I was you, I would keep my 7970 and upgrade the others components!!! You can go with the built of the previous poster but keep the 200$ of the GTX960 in your Pocket and use your 7970.
I find the 430W PSU a little bit too "tight" for MY personal comfort. ;-) I would personally go for a higher-watt PSU. Probably something between 550-650W...