I ran a 75 gallon, predominately SPS tank, for several years, with a Sunlight Supply Tek5, 6 bulb. Make sure you're looking at the Tek5 and not the Tek, as there is a difference. The Tek5 is actually made for reef tanks, and has 2 cords, 2 switches. The Tek is made for agricultural use and only has 1 cord, 1 switch. The hardware also isn't stainless steel so not as corrosion resistant with saltwater.
That same fixture, along with a 4 bulb Tek5, is now over my 200 Deep Dimension, also predominately SPS and 27" deep! I can grow any SPS I want, including high light demanding Acropora torts, on the bottom of the tank.
I wouldn't bother going with an 8 bulb Tek5 as it's wider than the 75 and will be a waste of light, spilling over. The 6 bulb Tek5 is perfect over a 75 or 90.
Here's a Flickr Link to my old 75,
75 Gallon Reef Tank - a set on Flickr
and my 200DD,
200 Gallon Deep Dimension - a set on Flickr