Wow, yes you will need a big ass fan for that space, though I think 2 x 745 CFM would cover it. Will you use all that space? If not, consider dividing it to segment fan needs - veg vs. flower. When it comes to setting up that space you will want to post to the indoor grow forum with details including the fan calculations so others can advise. I'm pretty sure of my calculations but there could be other issues to consider with a room that size.

If you were to segment likely you would create a smaller room for veg / mothers, clones, etc. You could get a smaller fan now and deploy if for your current space and then, once you move, divide up your new space and use the smaller fan for the veg/mother room. You would then just purchase a new fan to meet the needs of the flower room. Just a thought. Good luck with it. Keep us posted on progress. I'm building my new basement room at the moment. It is taking way longer than I wanted due to wiring, ducting, and framing issues.