Never ever buy a prebuilt. Build one yourself. Firstly you get the satisfaction of doing it yourself. Secondly you can pick and choose components that will be of a higher quality. Thirdly it's cheaper with a better price:performance ratio. Fourthly you can actually get better warranty since most parts offer anywhere from a 3-5 years and sometimes a lifetime warranty, much better than spending 150 bucks or more on an "extended warranty". If you post your budget I'm sure some people here, myself included, could help you pick compatible parts.
I mean right now I could say;
- Corsair Obsidian 650D Case
- Intel Core i7 2600k CPU
- LG WH12LS30 Blu-Ray Burner
- MSi GTX 560Ti Twin Frozr II GPU
- Western Digital Caviar Black 1.5 TB HDD
- Corsair Vengence 8GB (2x4GB) 1600 RAM
- Corsair HX750 PSU
- RAZER BlackWidow Keyboard
- RAZER DeathAdder Mouse
Might be a bit much at around 1700 total, but there's an option for you. You could save yourself about 100-200 bucks if you drop Intel for AMD (make sure you get an AMD motherboard as well), more if you wait for the new Intel and AMD CPU's to come out later this year (hopefully), and more further still if you go with a cheaper case, only a DVD Burner, an older GPU, slightly less powerful PSU, and a cheaper monitor. There's always options.