I have a 600 in a 4x4, a super sun 2 hood. It does it's job pretty well but I want to optimize everything. A 600 in a 4x4 is 39 watts a sq foot......while a 1k is roughly 60. I think changing to a bigger hood would be best as well....block buster or raptor6. Last run I did 6 plants in 3g smart pots, I want to do 9 or 12 next....however many I can fit. Eventually after that I would do co2 but changing the light would seem like the next step. Anyone move from a 600 to a 1k? Were you satisfied?
I moved from a 600 to a 1000. I was using a 600 watt hps in a 40" x 40" tent. I have since switched to 4' x 4 tents. Now I use a 600 mh/hps up through the 1st week of Flower and then I switch over to a 1000 watt hps. Yes, I was very satisfied with my results. I more than doubled the size of my plants. I went from growing four 2.5 oz plants to growing four 6 oz plants on four 10 gallon pots. A 1000 watt light is quite a bit brighter than a 600 so I would recommend it. The increased yield in the end will more than make up for the cost of a new ballast and bulb. I'm just using a 6 inch cool tube for my 1000 watt light with a 6 inch fan and it does just fine. As long as you do not do more than one light per fan you will not have an issue with cooling them, that is unless the ambient temp in your room starts to get too warm. These things put out some heat, so even in the middle of winter they can keep your room at a good 75 degrees without even having any heat on.