A 36X36 cube for SPS is actually a little difficult to light as many of the LED's are design for 24" x 24". Depending on how packed the aquarium is, you may be able to get away with two Hydra 52 HD's and having them elevated a little higher. If the tank is pretty packed, then you many need additional fixtures.
One good option would be using two of the
27" 15,000K MaxSpect Razors. Control-wise, the Razor features just a simple two channel controller that allows you to input 6 time set points, so it is not as feature-rich as the Hydra. However, due to it's larger size, it will do a better job covering 36" and the LED chips used, the spectrum and power output is great.