Quick question about sizing lights

im slowly building a cabnit in between work and college but its starting to look nice. its 4'x4'x4' so just a big square i bought some lowryder 2 seeds so plant hight isnt a question i was woundering with proper ventalation would a 400watt hps or a 600 watt hps be better. would a 600watt hps get to hot that close to my plants? should i just get the 400 and use cfl's as side lighting? how close can the light be to my plants? should i just use a T5 instead?

400 isn't enough light for that area. You'll need at least a 600. A heat shield will help with heat or even better a cool tube...When I had my 600, I had a heat shield an had it about 10-12 inches away from canopy an temps were fine. You might want to think about adding a foot to the height