This is my first time building a pc and my friends have been telling me which part to get and not get and im not sure if its all gonna work, especially that PSU. My Budget is $1200 US max. Here is my current build: http://pcpartpicker.com/p/1pa0G
I should mention I am using this as mostly a gaming computer but also for watching videos, reading, and lots of websurfing. Also a lot of those usb ports are going to be in use atleast half.
For gaming the i5 is an ideal choice since you are just gaming. Unless you are doing task that requires or takes advantage of multiple cores or HT, which in your case you wont since your just gaming. So I replaced that i7 with the i5 and replace the GPU with the GTX 770. As for the power supply I replaced it with the 650W seasonic trust me its more than enough. It fits the budget and it will handle all these components without it breaking a sweat. Did I not mention its a HQ PSU? Not only that its rated GOLD and its Semi Modular too. I mean its made by the best Seasonic, can't go wrong with them.
IMO, your PSU is fine. 750W is plenty, and Corsair is a good brand. If you want better, get a Seasonic (Corsair is Seasonic but with a 3 year warranty, where Seasonic direct is 5 year).
For a better gaming computer in your budget, you don't need the I7 CPU. Recommend the I5-3570K. You can overclock that for even better performance. Reference Tom's Best CPU's for the money showing that the I7 is diminishing returns for gaming.
With the money saved, recommend either:
1. Get an SSD - will have a much more impact on your system performance than I7 vs I5
2. Get a GTX 770 GPU