If I recall correctly, Alex at barefaced has talked folks out of the 3x10 setup in the past... Not enough of an improvement over 2x10 to bother. It was something I'd considered in the past myself, but Alex knows his beans so avoided it as soon as I heard he'd expressed his opinion (but open to being corrected by chris_b who has first hand experience!)...
The D800 does 2 ohms so why not add a 4 ohm Two10 to your pair of One10s? Ultimate modular setup!