I've used Jack's classic 20-20-20 for several grows and love it. What HPS is it? Digital ballast? If it isn't you can get a CMH bulb. Look at my grows with them. 400W is good for 3 x 3 I would go 2 or 3 in that. Start 5 or 6 seeds so you can nix males. I mix my own soil and it's in my threads too. It makes several bags worth though. I could help you with a smaller batch if you need.
This thread has a bunch of how I do stuff you could learn from.
Well Here Goes Again