How big is the room? If it's the common small space like a converted bedroom, you'll want the back of the monitors as close to the front wall as possible without actually touching. This will raise the quarter and half wavelength cancellation frequencies to a point that's easier to treat acoustically. Ideally you would get the monitors around 7' out from the front wall to lower the quarter and half wavelength cancellation frequencies to a point below what the monitor can reliably reproduce, but that's typically not feasible in most spaces.
Regarding the equilateral triangle; You may have already considered these factors but consider that the monitors should be placed with the high frequency driver elevated to ear level, and the convergence point of the equilateral triangle is ideally 10-14" behind your head while in the listening position. Also, if the room is rectangular (i.e. not square) then you'd ideally center the monitors on the shortest wall so that they fire into the longest dimension of the room, assuming it can actually function that way.