Which light system should i buy for my new set up?

I've been researching and and studying up on this for quiet sometime. so my question for you guys is. Which website can i order my 150w or 250w hps grow system from? for under 150usd. also is the purpose of the ballast just to up the volts coming from the wall to the light . or does it also lower the volts taking from the wall? meaning will my electricity bill jump very very high? cause i live in an apt and i dont want it to double from what my normal uses are. another question, i found someone online who lives close to my house who sells og kush clones for 6 dollars if. would it be smarter to buy a lot of those clones or start from seed? what would get me a bigger yield in about 3 or 4 months max from now?

HTG SUpply

would you guys use this in your closet for about 4-6 plants? http://www.htgsupply.com/Product-HTGSupply-400-watt-High-Pressure-Sodium-Grow-Light.asp

expect it to get hot, so plan on a way to cool it but yeah i would use that. Anyhow no one commented on power usage, i will be real quick with this, you can look at your electric bill and it will say exactly but most places charge 10-15 cents per kilowatt hour. That means 1000 watts for 1 hour. So to run your 400 watt for 2 hours would cost roughly 10 cents. A computer can easily run this much power.

I have this same light in a 3 by 3 closet..but then you need some kind of exhaust fan.. How tall and bushy you let then get will determine how many plants