As @PsyCLown if you have relatively large surface area to cover then you'll need a few boards, the ones from alibaba specifically meiju are very good, I currently run two boards per side in my 2.4x1.2, effectively 600 watts per side. I have now recently purchase an extra 240 watt per side bringing it up to 840watts (true wall watts). The reason for my expansion was due to form factor of my boards not covering the edges are they are rectangular.
Don't get me wrong these boards have done an amazing job at producing solid hard nuggets, but the hanging is a pain and as you can see in the corner and the center there are dark spots, however that is nobodies fault but my own. So I recently purchase two sets of the following boards
These boards are the LM301B spec didoes and the previous are LM 561 C . I will be looking at upgrading my LM 561 C boards to LM 301B/H when funds and time permits. The nice thing with these types of boards (I am more specifically referring to samsung diodes) is that you can run them cooler and softer and still get amazing results due to their efficiency per watt. You've got to stop thinking in terms of wattage and just because you have 10,000 watts you're better off, because that is nowhere near the case, it boils down as to how effective your fixture is at converting watts to usable light and that is where the umol/J factor comes in, a standard HPS is 1.4-1.8 umol/J, HLG 550 v2 Rspec is 2.6 umol/J. So immediately you can see that the HLG will outperform the HPS. The only draw back of LED is it does not have the same canopy penetration as HPS, but if you scrogg or whatever you'll be fine, even so you will still get huge colas if you don't scrogg.