The benefit is unlocked voltages and overclocking values on the chips (VRAM and GPU) so you can push your card that bit more, but you will need a serious watercooling setup to take advantage of this, or LN² or else you will more than likely fry you GPU or memory very quickly, and it isn't for a novice to really mess about with unless you have a very healthy bank balance and don't mind frying a few GPU's while you are learning the limits and how to setup and how far to push it.
My advice is not to do it, if you want to push your GPU, download the latest version of Afterburner, and go watch some YouTube videos and read some guides, but here is another warning for you, even Afterburner can fry your VRAM and GPU very easily if you push the volts up too much or don't have adequate cooling.....
At the end of the day, the choice is yours as to what to do, but myself and OC3D will not take any responsibility for you damaging your card and rig from doing this.