Thats a good build, But most people I know prefer windows 7 over windows 8 and say its not worth getting windows 8 before the 1st service pack.
As for the gaming side of things your probably going to want a little bit more powerful graphics card at around the same price
the GTX 650 -129.99 - 119.99 after rebate, It even comes with assassin creed 3 for free
http://www.newegg.com/Product/Product.aspx?Item=N82E16814130828
This card is much better than your current HD 7750 for only 20$ more I would go this option
This is a comparison of the 2 graphics cards http://www.hwcompare.com/13468/geforce-gtx-650-vs-radeon-hd-7750/
If you want a Radeon card then you can go the HD 7770
It is better than your current card by alot and is prety cheep -119.99 109.99 after rebate
http://www.newegg.com/Product/Product.aspx?Item=N82E16814127687
This is comparing the GTX 650 with the HD 7770
http://www.hwcompare.com/13467/geforce-gtx-650-vs-radeon-hd-7770/
And this is comparing the HD 7770 with the HD 7750
http://www.hwcompare.com/11880/radeon-hd-7750-vs-radeon-hd-7770/
Also may I ask what is your budget, I am also a young computer enthusiast that is currently building his own computer (im 16)
Good Luck!