No one has mentioned to you that it is important before selecting a GPU to be sure that your PSU will have enough wattage to power your card
this will help.
The R9 270x will require a psu with 24A on the 12v rail and a 500W psu minimum
The gtx 760 will require a psu with 30A on the 12v Rail and a 500W PSU minimum
be sure your psu will handle both of these cards which ever you choose
Both are good cards
the 760 is a great card m8 , worth saving for , there won't be much you cant play with that card