Your GTX970 is very power efficient and normally should have about a 550w psu.
Not knowing your language, I searched for "Seasonic" which is one of the best quality power supplies.
I would use the 620w unit. That will allow you a future upgrade to a GTX980 or even a stronger follow on.
http://www.pik.ba/artikal/12117382/napojna-jedinica-seasonic-ss-620gb/
If budget is a real issue, the 520w unit will run just fine, Seasonic is rated conservatively.
Other options that are good are Antec and XFX