cabinet design?

I am building a cabinet that is 3'X3' by 4' tall. I will be using a ScrOG style grow and soil or hydro. my question is, will a 400 hps light be too much? do you think that my cabinet will over heat? and is there any way to make your own air cooled lighting system or is that something that you have to buy? I plan on having 2 fans, one intake down low and one outlet up high. Also how may plants will fit into this space? its all personal use so I want to maximize the potency as well as the amount. any help or comments would be helpful, thanks.

6 plants tops. 4 may even work the best. 400w wont be to hot, IF you have adequate ventilation.

hey thanks!! what strains would you reccomend?? I was thinking about white widow just because I see a lot of people that seem to have great success as far as yield.