If you could follow the instructions in the How to Ask for New Build Advice thread, people will be able to come up with a more accurate answer for you. Specifically, intended usage, monitor resolution, and budget are very important pieces of information.
This looks like an ibuypower or cyberpowerpc (or other pre-built) build. Please be aware that this is a homebuilt forum, and most of the answers you get are going to be directed at building it yourself. You are also likely to get many posts telling you to build it yourself. You certainly don't have to, and you can take the recommendations given and attempt to apply them to a pre-built, but it's not always going to fit quite right. The reason regulars on this forum aren't interested in pre-built computers is because typically those businesses cut corners on some of the less-visible parts, such as the power supply, RAM, and hard drives. This doesn't make them bad people, but it does mean that the parts may not be as good as if you bought them yourself and built the computer on your own.
All of the above being said, 8 GB is overkill for gaming. The 5850 is a decent card, depending on your intended monitor resolution. The CPU you picked is a good one. RAID 0 doesn't really buy you a whole lot in-game.
Second that. I can already see huge problems. A poor quality PSU, 8 GB of mediocre RAM, a 5850 instead of a 5870 (or even possibly a 5970), a questionable gaming case, an unspecified 500 GB HDD and wasting money on liquid cooling.
Let me guess, that's about $1,600 right? Here's something similar, but better, for much less, and that's without even looking for deals: