Trying to score some deals on equipment any input please.

I'm looking at purchasing a used air-cooled hood but i want to find out Where i would go to get a Deal on a Fan and Filter Combo.

I think the size of the room is about 8 ft by 8 ft by 8 ft i think i would need a cfm rating of 400 correct me if i am wrong. i have been looking at cheap equipment and pricey equipment at my local hydro store.

the price of a 440 ish cfm fan is 210 filter 200. "canfan"
I look online for similar rated fans and i find stuff like this

http://www.ebay.ca/itm/4-6-8-Inch-Inline-Fan-Duct-Exhaust-Blower-Carbon-Filter-Combo-Speed-Controler/121593292129?_trksid=p2050601.c100085.m2372&_trkparms=aid=111001&algo=REC.SEED&ao=1&asc=20140211132617&meid=9abd3154fd5943af8cfc9e85ab8fe778&pid=100085&rk=3&rkt=4&sd=350675065979&clkid=7371801101274518694&_qi=RTM2067269

the filter seems small but rated for the fan. what should i buy help plz

would it be worth it to buy a used one and fill it up with charcoal myself ?http://www.ebay.ca/itm/2lbs-Air-Water-Filter-Refill-Coconut-Shell-Granular-Activated-Carbon-Charcoal-/290977688197?pt=LH_DefaultDomain_0&hash=item43bf9f2a85

here is a local deal http://www.bustan.ca/active-air-inline-fan-and-mountain-air-carbon-filter-combo-6-400cfm.aspx

moutain air 320 cfm filter with a 400 fan for $300