"Good wraith killing music"

Howdy, let's see if we can go two for two, I heard the song "Ring of fire" by Johnny Cash and instantly thought about John Sheppard. Then came to mind a story where I only remember one scene. Atlantis is about to battle the wraith, John gets in the Chair. Afterwards Rodney calls him Cash and John replies that it was "Good wraith killing music". Does anyone remember this story?????
Thanks in advance, finlaure