But CPU/RAM is the key. Rest all can take care of themselves! But in a way they dont matter too much.
Just make sure you have plenty of HDD space available. The files recorded from FRAPS or XFire and uncompressed video files since they eat up least amount of resources during the game. So a 10 mins recording can go up to 8GB-10GB.
CPU or RAM or both?
I don't want the game or the video to lag.