https://www.youtube.com/watch?v=7WQxr59KRto
Watch this guide, realise how easy it is and then use his list of parts to build your own, modifying it to suite your needs (and save yourself a bit of money). From what he recommends I would recommend on also picking up an SSD as well to install your OS on. The graphics card he recommends has very good performance for the money but a 280x is not that much more either. The FX6300 is a solid processer which will handle anything you throw at it and does not cost a bomb. Performance wise it is comparable with the older Sandy Bridge I5s.
Just my two scents but it will be far more satisfying and cost effective then buying pre-built.