Get a 3x3 or 4x4 tent
Look at northerngrowlights.com and cobkits.com if your defo going to DIY, overseas means taxes ect and they are only fractionally cheaper so USA bought from the right people is about the same.
Cree COBS have come down in price but are still a little bit more expensive but more efficient at lower currents.
Citizens COBS are cheaper and better for higher currents.
Veros are reasonable prices but I don't know much about them, I believe the new generation are pretty good.
Either way with COBs you can light up a 4x4 with less than 600w. You can light up a 3x3 with about 9 citizen 1212s which cost $13 each ran @ 1050mA which would only come to 350w at the wall and would be lots of light, you could go lower still and power them @ 700mA and be using less than 250w. Factor in around the same cost per cob for the heat sink or more if you go higher wattage per COB and work out how many drivers you would need. Can be done at a reasonable price but its amazing how the little things like wire, aluminium frame, TIM, connectors, adapters, lenses ect can add up.
The wise choice would be to have the power if you need it and dim them down in the hot months.
Same applies for the fan you already have, get a night and day fan speed controller and let it manage the temps. A 6" fan turned down will be quitter than a 4" fan on full. Acoustic ducting will help.
I would be building a false wall at the back so your tent is not in view when you open the garage door or getting some large wardrobes or something to disguise it. You could just grow in a large wardrobe or build something that looks like a tool store.
Get yourself a work bench and a hobby you have reason to be in the garage for.
Anyway if your going to do it regardless just be safe as possible, think about all challenges, where will you extract your hot air to? Where will you harvest and dry
If you have not already done so I would delete the photos you posted, you might need to ask forum mods to do that for you.
Good luck
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