@Randomblame .. basically to sum it up, to cover a 5x5 space I'll need 675w regardless of if I get 40 or 80 strips?? I was under the impression the more strips the less wattage needed for some odd reason lol .. then there's no real significance of getting double YES the efficiency increases but I still need 675w and it might increase yields like what 10%?? 40 strips vs 80 lol??
You could use an HLG-600H-54B for two 2x 5' trays. Each tray covered by 20 or 40 strips depending on the efficiency level you want to reach. Each 20 strips mounted on an alli frame to cover one tray with ~300-335w. Wall watt depends a bit one the driver because their max current is a bit different. But minimum should be +600w.
The difference in yield is marginal maybe 1-2%. The difference between 2,9 and 2,8μMol/J is 3,4% so in the best case you would get 3,4% more. But higher efficiency means always lower forward voltage. The voltage with 40 strips would be ~0,5v lower at 300mA. 50v x 13A would be 650w, 49,5v x 13A would be only 643,5w. That means the efficiency gain is always splitted in more light on one side and less power consumption on the other side.
That means with 40 strips per tray you would see between 1-2% more light(yield) and between 1-2% less power usage.
2,8μMol/J is already to notch in my book. My own fixture is just one year old and reach maybe 2,6μMol/J, with 2,5 I would still be really happy. Compared to the 1,9μMol/J you would get from CMH that's already a huge improvement.
And low driven LED strips are predestinated for your stacked tray system. The only issue I see is with stretchy sativas but there are so many strains out there you could still use you would need hundreds of trays to try them all in one life time.
Unfortunately my cab has only 66" height and thats not enough for two trays incl. res but I will maybe create something like a sun cloak next to make as much usage of the available height as possible. These LED stuff makes addicted pretty fast, bro. Every 2 years I want something new and the "old" light gets sold. But a good LED light pays themself pretty fast so there is no loss. Even one year is enough. Growers switching from HPS to LED's have the costs back in within the 1st two runs just because of up to 50% more yield. And you stacked system uses the available area to a maximum. With the right strains you can expect up to 500g regulary per 300-335w tray.
great minds think alike they once said 
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