i would invest the money to build another room in climate controll for the room you have, then you can grow 12 months out of the year.
the room you have seems plenty big enough for about 2 dozen plant maybe more maybe less but 6x8x8 is a pretty good sized space, maybe invest in 2 more 600w HID lights and you should be able to put all 12 buckets to use if not more
if your seedbank is on vaca till the 29th of feb then cancell the order and order form the attitude, i have ordered from them and all went well. you will have your beans well before the 29th when u expect yours to be shipped.
i really dont know much about hydro, all i know is invest in a good PH meter and a good PPM meter these ar eessential, but as you said you have a few years exp whit this system im sure you have all that shit.
so baisicly what i would so is i would get a couple more lights (unless you only plan on doing 5 plants to a time) then your 1000w should be fine, do some LST so you can get your light at a distance where you are utilizing yoour lumen output more efficiently and you will get a better yeild with a propper LST
gl and happy growing M8