I disagree.
Search the site for econolight 150w hps, the ones that are $20 (if you are in the usa). People pull off great grows with them just like any other HPS. The trick is fit the right lights to the right space. You're not growing 4x4 with one. 2sf is about right but the best thing to do in my opinion is get more 150's if you can get them at that price. Three will do 6sf just fine, and make you some tasty nugs.
It wouldn't make sense to buy 3, for that money you probably could find a 400 somewhere (used), but two are $52 shipped and you already have one.