Even after flashing a custom BIOS, my GTX 780 still throttles when running Furmark (and that's with the Power Target at 300% and the temps hovering at only 65c). There's simply no getting around it.
Like I said: "A more efficient card = less throttling = your overclock actually means something. You should be overjoyed at these power consumption figures if you're overclocking"
It still depends, if they only give it a tiny voltage headroom, you're still SOL.