Is my system good enough to play latest gaming in High Resolution?
The Radeon 7850 can match and beat the GTX 580 in a lot of tests, so yes.
I don't have any plan to OC yet but can i OC with p8h77-v motherboard?
Yes - but I'd personally get a different case and ditch the fans. Wait until you get your case and then see how your air flow is setup before buying more.
This is what I'd suggest: http://www.newegg.com/Product/Product.aspx?Item=N82E16811119233
Is it nice to have a cooler even though I don't have plan to OC CPU in term of $$$/performance?
It will definitely help improve your system's air flow.
What parts should I upgrade in the future ?
Only thing will be when the price drops - add a second 6850.
Also help me rank my system from 1 to 10 .
Change out the case with the one I suggested \and I'd say it's a 9/10.