I need a veg box. Any suggestions?

Hello folks, If you click my signature it will take you to my first log and you can see the space I am growing in now. In that space, I plan on flowering 2 plants at a time at about 3-4ft tall. My problem is I need a veg room so I can keep my crop going. Do any of you have any recommendations on how large it should be? Here is a couple of things you may want to know in order to get a better idea of what I will need:

1. I use CFL's. Probably (3) 6500k and (1) 2700k, or (6) 6500k and (2) 2700k.
2. I want to use 80mm or 120mm fan/fans (dont know how many I will need).
3. I use soil.
4. Need to have room for 2 plants in veg and 2 clones at all times, about 2-3 weeks age difference.

I was thinking something like this, but I dont need it to be that tall. Anyone have any suggestions on how I could constuct my own, similar growtent? 100% Reflective MYLAR GROW TENT Aero Garden tent BEST! - eBay (item 300273623784 end time Nov-22-08 19:38:30 PST)

Im basically looking for some dimensions and some ideas about materials to use. I want to go as cheap as possible. Feel free to throw some ideas around. I am open to anything. Now, this bowl is calling my name

Peace guys!