how big do you intend to grow them? several good fans and filter combos will help with the heat and smell, if you plan on keeping them short 2 400's should be ok.if it was me and i had 16 med.large sized plants i would be using 3 600's with wide reflectors and air cooled hoods linked together. and I'm not sure if i really understand y you wouldn't do cfls to start. cfls are cheap....... like several hundred dollars cheaper than any hps systems. ok i took this off there site..."whilst the 16 and 20 plant versions are 122cm x 110cm x 45cm tall (including pots). " this is a better way to go about this question,how long is this system in u.s measurements,length and width?? this is the most important question.