Can I and Should I upgrade my GPU

What can I upgrade to? Well a GTX 760 fit?

 


The 120 W (TDP) GTX 960 normally only requires a high quality 400W PSU. No cheapies.
http://www.geforce.com/hardware/desktop-gpus/geforce-gtx-960/specifications
But, yes, a bigger PSU will allow for a bit more upgrade in the future. But as Tradesman1 points out, be sure the card you finally decide on fits the room in your case. Usually length is the only issue.

Edit: I just realized you were asking about the 760 not the 960. Yes, a 500W is good. http://www.geforce.com/hardware/desktop-gpus/geforce-gtx-760/specifications
But the 960 is faster.