pc grow box,first time!

hello people,thats my first attempt to grow in a pc case and i have some critical questions about what equipment i have to choose.i have a pc case wich actually are 2 cases wich i made 1 big case.im going to put 2 big fans for intake and 2 for outake.the size of my pc case is 70cm(H)-40cm(L)-17(W) i want to grow maybe 2 plants of white widow and my BIG question is what lamps i have to take,hps or something else will be better?i was planing to take one 150watt hps but i dont know exactly what is the preffered distance betwin the lamp and plant.im planing to make then about 50cm high but you have to tell what is better in my case.
Thanx from sunny Greece!!!