I like DWC. Since my grows are small (4-8 plants) and I do perpetual harvest, I use individual 5 gal buckets with no main reservoir. This way I can control the ppm of each plant individually and also raise or lower the buckets to keep an even canopy.
I recently bought a 10x50' roll of 6 mil Panda film on e-bay for $60 and the shipping was free. It is worth it to buy the 6 mil rather than the 3 mil.
Since you have 9' of height, you should consider a separate cloning/seedling/vegging area on the top part of the closet. Fluoros will do okay in that part of the closet. I really like the T5 fluoros. I think that they do quite a bit better than regular fluoros. A 400w HPS would give you enough light to produce a great crop in a 3x3 space. Make a DIY cooltube. There is a plumbing product called a "no-hub coupling" that works excellent for connecting ducting to the pyrex tubes. A no-hub coupling consists of a rubber coupling and a stainless steel sleeve with 2 hose clamps. Use only the ss part. I use a wrap of some kind of tape around the glass before tightening the hose clamp. In a cab this size, ventilation is critical, so plan for cooling.
It is almost impossible to do too much reading, studying, and planning.