Another thing AZN... When you want more info on something someone tells you just do a search on it. The search button is in the toolbar at the top of the page. Just be careful and don't get caught up and forget to sleep :stoned:
You can get a product at home depot that is 97% reflectiv and works well. It is an insulating bubble type sheet. You will find it in the insulation section if they have it at your HD. It looks like those little packing bubbles you can pop but is silver and rolled up. Alternatively if it suits you purpose as it does mine you can get 3/4 inch thick insulation that is for reflecting sunlight. It is a 4' x 8' sheet of foam that has 97% reflective material bonded to both sides. Either way you go it will be using whatever light you provide to it's fullest.

CFLs... These would be the best bet for anyone with heat issues or budget concerns. It is pretty easy to get 23 watt(100 watt replacement) bulbs in cool white(veg) or warm white(flower) They have them at HD you would really need quite a few of them though. Another alternative that is more pricey is the envirolight 200 watt. You could use 2 of these. They would produce less heat than 400 watt HPS but need to be kept closer to your plants and require more maintainence to keep the plants from groing into them and burning. If you decide to do the HPS thing research cool tubes. This will help dramatically with the heat issues. Some growers use T-5 lights. T5s are flouros and I have read that some growers swear by them but again any flouro needs to be quite close to the plant to be 100% effective.

Tell us how you are going to deal with heat and how long you plan to veg your girls before switching into flowering mode????

-Jay