Look man, there is a right way to do things and a wrong way. I'm not one with lots of money either but I would rather purchase a fan filter combo which you can get for less than $200 if you shop around..htgsupply.com. hint hint. I don't think its worth the risk of using a fan that is not designed for what you are wanting to use it for. Plus duct fans are specially designed for perfect airflow to get that hot air out as fast as possible while providing a good suction of air to come in. I just bought everything little by little and now my setup is as follows:

1 HPS 400 watt S51 type ballast with reflector and bulb.
1 3x3x6 hydrohut mini
1 170 cfm inline fan with elf filter scrubber
4 GH waterfarms
1 sunleaves 4 outlet air pump for lift systems
4 single air pumps for reservoir airstones
floranova grow
floranova bloom
6" clip-on fan for air movement on plants (still on the way)
1 heavy duty digital appliance timer for fan and light