Those 600 per plant is optimum . a 1000 is over kill . unless its veg for 6 months and topped. 3 times. Plant will only decide to soak up so much light. I suggest side lighting with led in the middle and bottoms of the plant . this will add yield
If you have the space - 1K's are
never overkill! You wanna run sativa's or high sativa cross's? You
better run 1K's!
Why do you think that 2 600's are suggested for a small space over a 1K? MORE available lumens/ Umol or how ever you want to put it!
Why do commercial ops run 1K's over 600's (Unless they invested in COB)? What about a 1K DE?
Keep your 600's O'conner!