Ideally you want to researh what carbon filter you would require for the space and number of plants, and then match the fan to the carbon filter, while taking into account the size of your grow box and how the fan in question will work with regard to the rate of air exchange. I'm afraid i can't be much more help than that, i simply bought a ventilation kit and it did the job fine so i never had to research any further into buying new and more appropriate equiptment.
For your space though, it might potentially make more sense to go with low power fans such as computer fans, and then an ozone generator. But again, not something i've atually looked into much.