I would run 2x SGS-160's over 4-6 plants. They will fill the area with light, but your main concentration of light will be a 4x3. You can stagger the lights, so they are not hung symmetrically to help cover. Having a core coverage of 4x3 in a 4x4 is not a bad thing at all, that gives you space to run a tower fan and anything else(climate control, timers, wiring, net mounts/SCROG, etc) without interfering with core coverage. If it was my money, I'd go for two SGS-160's in a 4x4 or 3x in a 5x5.
A couple 4ft T5's would be a very good addition to a 4x4 with two 160's, they can be ran closer, or even below the main canopy(vertical corner lights) to increase total production.
A couple 4ft T5's would be a very good addition to a 4x4 with two 160's, they can be ran closer, or even below the main canopy(vertical corner lights) to increase total production.