I know I am late to comment, but as the other posters said the orbit is not a good choice if you want corals. I wrote up a nicve review on my thread the other day on it.
I have it over a shallow 40b tank and it cannot grow
sps and
lps is just about the limit for it. My nem is reaching for the light as well, def not enough for him. Over a 75g it would be almost useless. :-(
The tao unit mentioned early on is a great choice as it dims and will keep anything you want to keep as far as lighting goes.