But with the grip, it does give you that extra fps. I have not tried it and still don't need that yet.
The grip does not increase speed on The D7000/600 or 800 it just holds another battery and they switch from one to the other when the first is exhausted....
increased FPS in DX is nothing to do with the grip......
The grip definitely does not increase fps on the D7000 as on my D7100, it gives longer shooting time and in my mind, improves the cameras comfort.
For clarification using the D800 in DX mode without the battery grip will allow you to achieve up to 5 fps in DX and 1.2x crop mode
Adding a Nikon MB D12 and AA batteries will allow the camera to achieve up to 6 fps in DX mode. Therefore the grip can increase the fps in DX mode unless you have a reference from Nikon that proves me wrong.