Efficiency is nice. But, don't be blinded by it. To increase efficiency, why not use 300 1/2 watt'rs? or 600 1/4 watt'rs? ......
Drivers may be 60-90% efficient too. So, going overboard with LED count and wasting it with a driver trying to drive this array.... may not be a good idea. You need to balance what you're trying to do to make it work.
Your plants need a certain type of light spectrum to grow.
Your best bet is to research the type of LED, regardless of efficiency, that is needed to make your plants grow. All the efficiency is wasted if the 'tomatoes' don't grow in your light.
And, once you find the LEDs that you need, build your lights around them.
From the sound of it, you're looking for a large light panel.
I think it would be a good idea to build yourself a 'small' light to see if the bigger project is feasible and within your budget.
Start with 10-25 LEDs. You'll have to research brands, like from Cree or Luxeon..., the color output of the LED, the driver like Meanwell or Xitanium.., your heatsink(big aluminum block or extrusion, your LED wiring(series parallel combination)... and put together the test light. If it does what you need, expand on it.
Definitely read up in the aquarium LED section in some of the online aquarium/reef/fishtank forums. They seem to build some higher power LED lights. You might be able to copy/multiple some of their lights to get what you're looking for.
150 Cree XP-G's on a star would cost?
15-20 MC-E's or P7 sevens?
A 150w LED light growing panel off a website?
