What size will compliment my setup?

I have built a previous box but it is too small for what I want. I will however use it as a first stage box. This is what I have, and now want to build an enclosure for it.

Lighting:
2 x 4-Bulb CFL 23W Light Strip Length is 2ft (2700K & 6400K) - 1600 lumens each
1 x 3' Sunblaster T5HO Length is 3ft (2700K & 6400K) 3700 lumens

Total - 8 23W CFL, 1 39W High Output Fluro tube = 16,500 Lumens total

Depending on how the vegetative stage goes, I may add an additional 3' Sunblast T5HO for flowering.

Seeds:
White Widow

Nutrients:
Advanced Nutrients 3 part grow, micro, bloom

Soil:
MG Organic Choice

Ventilation:
Intake - 2 x 120mm Computer Fans
Exhaust - 1 x 5'' duct fan w/ carbon filter


I want to have a max height of of 54" (4.5ft) --- 4 ft max grow size. I am not sure what width and depth I should go with. I would prefer to stay at 3-4ft wide. I have no problem with cooling and staying between 70-80 degrees. What is the best way to mount my exhaust filter inside of the box? Should I put it at the top and have the intakes near the floor?

Any help is greatly appreciated!

hot air rises and you want cool air coming in from your intake fan

I personally would build it 60"x48"x24". It will give your plants a good amount of room and lessen the amount of heat buildup by having more area. Your exhaust fan can be mounted outside the cabinet if that is possible, or inside you could hang it high and secure to the top of your box above your lights. Make sure your intake hole is large enough to handle the air flow you exhaust fan will create. A fan can be placed outside to push air into the cabinet. Peace