Fan Question

Hereâ??s the set up:

2.5 feet by 3 feet by 7 feet.
600w hps ( i know its big for the space)
4 sativa plants in soil

Hereâ??s the question:

My problem stems from ventilation. I'm not sure which fan types to use. The fans at home depot are considered inline booster fans despite their cfm rating. Are these fans acceptable for ventilation purposes, or is it better go with a 3x more expensive squirrel cage type fan? Iâ??m thinking 2x 250 cfms, one which is directly in the reflector.

The cab is very close to a window.

What are your guyâ??s thoughts and advice?