The V2 unit has the fan add on to prevent overheating. It was a big problem on the V1 units, especially if it was in and unvented cabinet. I still suggest standing the unit upright for maximum air flow. The add on card is simple to install, I have detailed pics of the install process. Follow this link to get the pics:
http://www.abadss.com/forum/854-view...e-options.html