Help me out with my setup plz

Ok, so this will be my first grow. Im in the process of looking around on craigslist for a cab. I plan on getting something 2.5-3ft long, 2-3ft deep, 5-6ft high. Ill be sectioning it off so there is 3 feet of head room for my plant to grow, the top part that i section off will be where i house the inline fan and remote ballast.

Exaust/cooling wise i wanted to use a 4" inline fan with a carbon scrubber
I either want to buy this fan and make my own carbon filter(any suggestion on a easy/cheap diy that will work for a cab this size)
http://www.htgsupply.com/viewproduct.asp?productID=52557

or should i just get this combo
http://cgi.ebay.com/4-INLINE-FAN-CARBON-FILTER-COMBO-ODOR-CONTROL-SCRUBBER-/160441909586?cmd=ViewItem&pt=LH_DefaultDomain_0&hash=item255b154152

Will using this size fan work out for my grow space to keep it cool and odor free?
Also, a noob question, am i supposed to vent out the top section too? if so, whats the best way?
thanks

either fan will work well for you. but you really don't have as much head room as you think. count 8 inches for the pot and 12" to 18" between the light and your plants, with 12" for the light itself gives you only 3 feet for the plant without the fan and ballast.

and not sure what you meant by venting out the top section, if your fan is there you're venting, right?

True, yeah, the fan is going to be there, so i dont need to worry about the electrical room then.
So about 4 feet for the grow room should be good then? I wont be vegging them for very long.
thanks

you should be good to go

Thanks very much. LAst two things if anyone could help me out, how many passive intake holes should i use. And with a cab this size should i pull the air through the scrubber or push it through? I know its best the pull through, but will i be ok since im using this fan as an exhaust and using a scrubber?
thanks, i hoping to start getting all my stuff together the next couple of weeks.