100% vote for build it yourself. You get to choose your components and it WILL be cheaper than going with a company like Boxx.

There are many PC videos on youtube and other websites that can provide guidance. I've recenly finsihed building my own machine (simple hand made case as well) and have also built a Socket 2011 render machine for a friend recently.

Shout if you need some help. Where are you in the world? A few hints : Don't stint on a good power supply and good motherboard, these form the basis or foundation of your build.