You can MAX the quality on most games, at 1920x1080 @60FPS. You'll want to tweak the quality of some of the more demanding games to maintain your desired frame rate but even those will look almost full quality.
1) Recommend Windows 8 64-bit OEM ($90 USD), and Start8 ($5)
2) Tweaking tips for demanding games:
a) run game and FRAPS
b) Turn VSYNC OFF (or force with NVidia Control Panel)
c) Tweak quality settings (anti-aliasing, shadows, DOF etc) for best results at desired frame rate (either 40FPS VSYNC OFF, or 60FPS VSYNC ON).
I use VSYNC OFF unless the screen tearing bugs me (which it often does). With VSYNC ON I tweak so that I can maintain 60FPS at least 90% of the time, then I force ADAPTIVE VSYNC for most games.
**Again, I force Adaptive VSYNC for most games (you can Google why).
That's a really great gaming PC and you'll be very, very happy with it. You will need to learn how to tweak for optimal results in some games though.
Again, that's with a focus on VSYNC ON, or VSYNC OFF as discussed above, and Adaptive VSYNC is a great tool.
If saving some money is critical then I guess you'd have to rethink some parts. In the above build a difference CPU cooler is given for example. However, that cooler is NOISIER than the Noctua coolers; it's not "loud" it's just not silent. I've used both and the Noctua is so quiet when gaming I can't even hear it if someone stops the fans.
If you need to save a little money then I'd need an EXACT budget otherwise I'll just recommend your original build with the different Noctua cooler I linked.
Is the CPU Cooler you suggested same good for overclocking as the one in my gaming build? If you don't think about the price, which CPU Cooler would be the ''best'' for my gaming build with Asus Z87-PRO?