A pound for a 400 watt light is excellent , for a 1k hps, not so much if 1 gpw is the bar . I disagree strongly with not enough room to grow in a tent, I supply 5 patients with enough for 2 months off of one 40x 40 inch tent , this is not including the other experiment and production rooms . If they run through it quick cause there short on cash or whatever , I have them covered there too but they usually do not get the tip top of the iceberg so to speak,
In a tent the heat is the biggest issue you will face and you will need the best airflow you can get. for a 400 watt hps in an air cooled tent 1x1m2 I needed a 420 cfm fan for 76-80 degree temps , when I went to 600 hps it went up to a 700 ish fan and when I went up to a 1k hps I had to introduce a new vent carrying ac cooled air into it . I honestly would stick with 600 hps for smaller rooms as there more efficient then a 1k and easier to manage . Dont be told a tent is not productive , you may need to just be a little more proactive about it
BB