400w or 600w for 12.5 sqft.

Hi first post here. First grow. I have a 5'x 2.5'x 7.5' cabinet complete with a/c and good ventillation. I was thinking of a 600w hps to put in there. The guy at the grow store recommends I put a 400w. Heat vs. light vs. electric. any suggestions? I 'll be posting pictures and grow progress as necessary. Still getting it together. TIA,
dwarf

if u want more yield go with the 600w...enough to do 6 medium plants..

2x400W. Better coverage. They don't penetrate very deep into the plant, so short plants are the key. You should be able to get 12 in there with no trouble.
Fred

I decided to get a quantum 1000w. It has a dimmable ballast so I can control how much light and heat. I figure its also "future proof " if I change my set up

600w is right for the sq.ft but the form of the room is long and thin so it will not cover it right. 1000w is overkill IMO you're payin more than you really have to. you need 50w/sq.ft it will be good if you get a 400 and a 250

the longer the wavelenth of light the better.... like it has to be incandescent light ...vapour lights that have the watts but shorter wavelength and affect the grow high if you dont want the electric bill go for high frequency flourecent ( really bright and the wavelenth is long enough to give good cover) and provide heat via the ventilation with a humidifier ...works just as well and you can really cut down on electricity bill