Power Supply:XFX 550W 80+ Bronze Certified ATX Power Supply (£49.13 @ CCL Computers) Total: £49.13 Prices include shipping, taxes, and discounts when available Generated by PCPartPicker 2015-04-02 22:15 BST+0100
300 watts is not enough. A good 550watt power supply would be good for a 970. And you should really post the rest of your specs as well when asking people about power requirements.
Power Supply:XFX 550W 80+ Bronze Certified ATX Power Supply (£49.13 @ CCL Computers) Total: £49.13 Prices include shipping, taxes, and discounts when available Generated by PCPartPicker 2015-04-02 22:15 BST+0100
Yes you should post the rest of your system but I think it is fair to say with this setup you need at least 550w. A good idea is to look at this tier list:
It is really helpful. You're looking for a 550w or more PSU from tier one or two. My tier two choice was Antec TruePower Classic or Antec Edge if you want modular.