If you can get away with the heat, by all means get as big a light as you can. One of the reasons I used CFL's was that just 6 months ago, HPS systems were a minimum 300 bucks, but they are getting so cheap now, CFL's are not nearly as cost effective vs. hps as they used to be. They still create less concentrated heat, which is good for small spaces, and you can still move them all over and get them right next to the plant, but you can get an HPS with a cool tube and fans for about 400 bucks that you can place almost on the plants. Still steep for the average grower to start off with, but much cheaper then the $1000 these setups used to cost.