Would losing the back of the stand hurt rigidity? If not, I would get rid of the back and get a fan to move the hot air. If the back cannot be removed, I would think twice about the stand as Onkyo's are known to get very hot. I briefly had an Onkyo. It had vents on the sides, towards the back. I would feel more comfortable with more space to the sides if the receiver you're considering has the same side vents.