I think you should investigate vertical growing before you ditch the HPS lighting (if used efficiently of course.. vertically, I believe it is a more efficient method than using LEDs in terms of power consumed relative yield).
You ain't never hitting 3gpw hanging bulbs horizontally. Yet Heath came very close to that in an old colleseum grow he did going all out. When he's slacking, not using CO2, not using aero (instead his high performance hydro setups) he still hits 2gpw quite often.
Worth investigation if money isn't an issue especially. There are some decent prebuilt setups if you are not particularly handy yourself. Alternately you can just grow mini trees... I did that in 4x4 tents and yielded over a 1.5lb (minus smalls which would have been larger in a bigger tent with a little more space for your canopy relative the light). This was without CO2, growing from seed, 9 different plants, all with different nutrient preferences where I screwed up and burned them with excess Nitrogen having not grown them before and not knowing exactly what to expect.
I fully expect to increase that yield significantly this fall (per watt).
LEDs are inherently inefficient due to their projective nature IMO. They are not designed in the same way where light shoots out evenly from all angles like HIDs. That HID design is a huge advantage in terms of space and overall efficiency, despite popular misconceptions, IMO. You could do vertical with LEDs but you wouldn't be getting 600w of power from all sides as those panels are quite large and would never fit into the same area therefore allowing the space maximization. Granted with a large room you could do this, but the fact you are running 4 (minimum) panels vs 1 HID pretty much makes that idea stupid IMO.