If i was going to run 6 k worth of lights .. i would do it on a flip flop. 2 different rooms with 3 k in each room .. easier to deal with the heat, and like the rest said .. personally id go for the 1k hps .. better penetration, Any one ive heard of getting 2-3 lbs per 1000k is doing it with 1000k bulbs and ballasts.

And as far as hydro setups go .. im a big believer in flood and drain setups.. no root rot problems etc. that u get in the tube setups.. flood and drain is pretty fool proof.