Why go custom??  This is a commonly asked question when thinking about building a custom computer.  The vast majority of computers are built around the ATX (Advanced Technology Extended) standard; it was developed in 1995 by Intel.  It was put in place to ensure that any component engineered by these standards would be interchangeable with those of another manufacturer.  Many large manufacturers use proprietary components which do not comply with the ATX standard and as a result if you want to upgrade a component then you have to check with the manufacturer for a list of compatible parts.  We believe that you should be able to choose the manufacturer, and the specifications that you desire to have, not what parts the manufacturer dictates that you are allowed to use.  When you build a custom machine, you have the opportunity to select each component that goes into your system.  It makes your computer actually feel like it is yours, not just the same cookie cutter system that everyone in your neighborhood has.