its not really a prebuilt pc. this is a customizable pc. prebuilt is more something you find in Best Buy...
you should now customize this selecting components that meet your needs. once you think you have your rig, post it here and we can critique it. don't forget to tell us your budget, what u will be using it for...etc...
Inzone is right. With all the default settings, you should be more than fine with gaming performance. It won't be incredibly future proof, but it will certainly work for a while.
For instance, that GPU (radeon 6850) could be moving on its way out in the next couple years.
There are also various places to save money, which you would be able to find more easily if you bought each component individually. For starters, the rest of that default set up does not by any means require an 800W power supply. Maybe if you plan on adding two more GPUs, but I doubt you plan on doing that. You probably only need ~650W in a PSU considering the rest of the build, and even that will overshoot what you need. But with PSUs, overshooting a bit will never hurt as much as undershooting.
A case of that price probably isn't necessary, unless you REALLY like how it looks and its features.
I would be careful using a site like cyberpower that gives you a custom build like that. I really don't like how they don't show the price of each individual component. Because the truth is that if you bought the components and made the same exact build, but you did some research and bought all the parts from different vendors, you would probably be able to save a decent amount of money.
But if you like the hands-off, customize approach, go for it! And if straight up performance was your only concern, but all means, ignore my warnings. You don't have much to worry about with being able to play the games you want at high quality.