400 or 600 watts

I am about to buy my HPS my closet is 5ft 2" wide 6ft deep and 81/2 ft tall. I have a small A/C vent on the cealing but no exhaust I am willing to cut a hole to the attic. I am looking at the 600 watt digi HPS/MH set up or just a 400 watt HPS only $20 dollar diff. What should I do for the temp control other than A/C its a bit cold out? Whats my best option for air circulation/smell? and what light would you go with? I have been vegging way to long and I need to flower sooon! HELP AAAAAAHHHHHHHHH

The 600's are the best all around value,as you well know they dont cost much more than a 400,plus their lumen to watt ratio is the highest between 400,600 & 1,000 watters.

For temp control think about getting a vented hood,right now that its cold out you can remove the glass from the hood & the heat from the bulb will easily heat the closet.

In the summer time put the glass back & vent hot air from the light hood into the attic.

If it gets too cold in the closet at lights out just use an electric heater with digital tempature selection,put the heater on a timer & have it set to come on 15 minutes after lights out & have it go off 15 minutes before lights on,this way you wont need to use a seperate circuit for both high wattage devices.

Im not so sure i'd jump on the digital ballast bandwagon,standard magnetic ballasts have a much longer lifespan & a proven track record of being ultra reliable,many digital ballasts have a very short lifespan,the electricity savings from running a digi ballast are not that great to start with.