I believe a 600W HPS would be about right for a 3X4 (maybe could get by with less light), but that comes out to about 50W/sq ft. So any light source LED or HID or CMH would need to be about at that power level. With 400 watts your potential harvest as a beginner will likely be less than .5 gram/watt and that is about every 3-4 months a harvest. So after 4 months (once you get setup) you might see 150-250 grams if the run finishes.Only concern I have for your needs is the oz a week,its doable but hard with a small tent and setup,with 1 tent you can't go perpetual so you would be harvesting every 3 months roughly needing over half a lb to get by. Just a heads up and something to think over.