X51 R2 upgrade GPU questions

I need some help here . I'm currently using x51 r2 with GTX 745 GPU ,and I wanna upgrade to EVGA GTX 970 sc . But the consern I got is about my power supply ,is it gonna be enough wattage for 970 ? And I've searched so many time on the internet,the post date of all of them were like 2 or 3 years ago . I opened the case days ago and when I look at that 745 I was disappointed a bit ,it's so small not even bigger that a SSD or a cellphone ,and I can't play GTV V or some other games on a high setting ,only medium to low graphic setting ,it's quite a sad thing ,don't u think ? i don't even know how much wattage for my x51 ,so pls help . Is it gonna be enough wattage if I want to upgraded my GPU to 970 sc ? Or do I have to upgrade my power adapter to 330W ??