Larry, Don't think the 6 fps is in your menus. But I could be wrong. That's the advertised rate in Continuous High release mode.
From p78 of the Nikon D7K users manual, it says "When the shutter-release button is pressed all the way down, pictures will be taken at 6 fps in continuous high speed mode, or at the frame rate selected for Custom Setting d6 in continuous low speed mode. Frame rates may slow when the battery is low.or vibration reduction or auto ISO sensitivity ISO sensitivity control is on."
Good luck with your decision and good shooting. Best regards, Tom
"Nothing can be recognized without light and shade. It is only through the eye, the window of the soul, that we can truly understand the complex workings of nature." - Leonardo da Vinci