Help designing my grow cab?

Heading back to Michigan here soon, so I plan on hitting up the hydro store and getting myself a decent setup. Currently using an aerogarden and some CFLs. Just popped it on 12/12, but I know I wont be getting nearly the yield I want.
So my plan here is to build my own cabinet, so it can be any size. Would like to have a veg area in the bottom, under some CFLs. Then on top having a 400w HPS for flower. I have a $500 budget, but plan on buying a used ballast, cause everyone and their brother gave up on growing!

ANYWAY. I need help designing the cab.
I want the ideal size for the light footprint. Will be running DWC with a 400w cooltube (I don't want one, but it gets hot here and I don't want to worry about temps, any other good way to control it?). I don't know what size fan I should use for this cab. I have tried to kinda read up on grow room design, but haven't found anything quite like what I want.
Considering a scrog, but not sure...
Really, don't know what I want. all I know for sure is I will be building my own cabinet. Probably want 6" tubing, but would go with 4" if there is a significant price difference. 400w HPS. Hydro cause its cleaner, and DWC seems to be the easiest method... Not sure how many plants I could fit into the cab, since I am unsure of the size. I know, it seems like I didn't do any reading and just came asking questions, but I just want to be sure I get all the stuff I need while I have easy access to a hydro shop.
I want to yield about 4oz/month if possible, since thats about what I smoke, but anything will be better than buying it all!

Thanks for any help. If someone could link me to a similar grow I would appreciate it as well.

You smoke a Qutie every month??.... damn you smoke alot. lol.. and actually DWC is not the way to go as a noob in my opinion. Heard Coco is best for rookies or soil becuase you have more room to fix error..

I have a veteran pot smoker living with me, so I was including her as well haha.
As far as easiest, I meant setup wise. I would prefer growing in soil, but I think a hydro cabinet would be easier for me to use. I'll wait till I have a room before I start with soil.

only advice i can give is dont try over kill with ventilation. me being a dumb ass bought a 8 inch inline fan for a 3 plant grow 400 watt hps. didnt know how much air they can really push and wasnt the quietest. if you had the money this would be pretty neat http://www.ebay.com.au/itm/SECRET-JARDIN-DARK-ROOM-II-TWIN-GROW-TENT-90X90X210-/200703745418?pt=AU_Seed_Starting_Hydroponics&hash=item2ebae01d8a small but i think it would be big enough for scrog.