Honestly i think that light is a bit small for a 5x5. I would probably run it in a 4x4 and if it got my plants crispy, raise it/dim it. Im sure it grows great plants in a 5x5, just could have a little more potential with more light. (i think, i could be completely wrong)
Hell this summer ive got far to much time on my hands so i might as well grow. Im running a 600w de hps bulb because theres no way i want to deal with the heat coming from the 1000, especially running @ 1100w. I will be keeping my plants smaller and they definitely wont be wall to wall, 70-80% capacity max.
But you hit it on the nose, lighting up a 5x5 with led is EXPENSIVE. That light is 1100$ down here and its what i would consider the minimum for a 5x5.
In the future i will only be growing when its cold outside. All that heat from the HPS just ends up heating the house so nothing is wasted.