$600 Gaming PC help!

Could someone throw me together a $600  gaming pc? I live in canada but if the prices are cheaper anywhere else I have an address across the line. I will be mainly be using it for gaming, I perfer intel cpu's, and the case cant be a piece of crap. I have a few ideas for parts but I'd like to see what someone else could suggest. 

Thanks in advance!

http://www.youtube.com/watch?v=fX_QxnuG1XM&list=UUXGgrKt94gR6lmN4aN3mYTg&index=6 

here, and if you'd rather have an nvidia option, i'd suggest you check out the gtx 660ti

http://pcpartpicker.com/p/uZHA 

Build from the video above. I switched the PSU from 430W to 500W. AMD recommends 500W for the 7850 and it's only 5 more bucks anyways (at the moment). Good build but about $50 over budget. You can save some money by going with a regular ATX case and regular ATX mobo: http://pcpartpicker.com/p/uZJt

Do you need to buy an operating system?

Thanks for the input guys

 

Np (: come back to this thread if you still need help