Boost isn't a Waste? My GPU overclocks from 980 to 1110.5 MHz in games
where it is needed, instead of running on 1110.5 24/7. We're talking an increase of 13-14%.
I own a GTX 660 reference which should overclock itself to 1033 MHz, as I just told it doesn't. It goes even higher and if I had an aftermarket cooler on it, it would overclock even higher because of the better cooling. Don't believe the specs.
So with boost you save more power, you save heat and prolong the life time of the GPU, compared to a overclocked GPU.
But it seems as if you will push it to the edge, so you might just be better off with the normal one.