Hey, I'm no expert, but even with a 1000W in a 2X3X6' cab, you couldn't approach the light intensity of the sun. If you can keep the temps within an acceptable range, the added intensity would only give you fatter, denser buds.

I also agree that there are too many other factors involved to say how small a cab you could put a 600W in with a 500cfm fan. Ambient temps are a real consideration. If you put that set up in a cool enough room with the light vented from outside the cab, the cab size would be smaller than you would be able to grow in effectively.

Best bet for a height restricted cab would be SCROG.

So, I'm just rambling because I am f*ing STONED! Ha Ha Ha Ha!!!

~Rock~

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Silence is a true friend who never betrays. ~Confucius~