Well, first things first - if you are growing for personal use, how much do you use? Most smokers I know are about 1 gram a day AVG (less some days, more on weekends, etc etc). This is 1 oz a month roughly - meaning if you grow from seeds in a single grow area, 1 batch at a time (roughly ~100 day cycle from seed to cured-ish) you'll get 2.5 harvests a year - so you'll need to pull roughly 6 oz per harvest to have 1 oz a month.

Even a first time grower, if they pay attention, should be able to get 6-oz from a 400W light and say 2-4 plants. Even 1 plant if you have it positioned right, large enough container and good temps, although this will be a BIG plant...