So i'm thinking of upgrading my pc I have an i7 4770 and a gtx 645. I'm going to be getting gtx 1070 https://www.amazon.ca/EVGA-GeForce-GAMING-Graphic-08G-P4-6173-KR/dp/B01GX5YWAO/ref=sr_1_4?s=pc&ie=UTF8&qid=1469853928&sr=1-4&keywords=gtx+1070 and a 750 w gold psu https://www.amazon.ca/EVGA-SuperNOVA-Certified-ATX12V-220-G2-0750-XR/dp/B00IKDETOW/ref=sr_1_1?s=electronics&ie=UTF8&qid=1469854102&sr=1-1&keywords=750+psu was wondering if id need a bigger psu or if i need to upgrade anything else with this 1070. Also I'm wondering if this is the 1070 to buy. there are a lot of models out there on amazon. This one seemed the most affordable. I don't understand the difference between the different models