hello mate.. some people aim for 1 gram per watt.. im sure that what ur talking about.. its not easy. it doesnt nessesserily depend on number of plants.
i have achieved almost that, in soil. it depends on too many factors, i joined this website and read, read read, for ages, before taking the leap. the people on here can and will help you every step of the way.... good luck, more info and your opening move would be helpfull...