First Time Grow Some Help Please!

Hey everyone, this is my first post, just want to say hi!

Anyway i have a 600 watt HPS light and ballast from HTG supplies and i was wondering if it will be overkill. The size of the room i plan on using is 52"x36"x84" and i only wanna grow about 4 to 6 plants. Would i be better off downsizing to a 400 watt? I dont want my electric bill to sky rocket so is the 600 watt overkill? Thanks for any advice.

if u can afford the bill then get a 6 if not go wit a 4 or 25.im goin to giver them my money in a few weeks,then ill be all set again.

anybody else