I have 2 SF4000 in my 8x4 tent, current meter (self calibrated) shows 890W. I have no complaints other than the dimmer box on the older one of the two makes some noises at the lowest level (I just avoid that).
So, to be clear, is each light a one off or do you have some standardized models/designs. These days, everyone is basically using good diodes, its the rest of the parts and the design that makes or breaks a light. Personally, I don't care for either the large quantum boards or the multi-bar setups. My favorite design so far is the single bar designs that fit more of a florescent fixture setup like this Mars Hydro light...
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I'd rather rock a bunch of these and space them how I want. Only issue, this model specially is over priced for its output.