If I were you I'd go with the 165cfm fan. A couple 90 degree turns in your ducting and that extra cfm gets chewed up fast. And while once every 2 minutes is the minimum exchange... you don't want the minimum harvest right? I suggest to most people at least a 2x per minute exchange. I use a 400cfm fan in a 175cuft tent and it vents straight out. When running it on high I can achieve a 3 degree difference between the temperature under the lights and the intake temperature. So for you the 160cfm with a few turns in the ducting will guarantee a 2x per minute exchange rate, and might be able to hit almost 4x per minute. Really, you can't move too much air... And that 160cfm fan will do better with a carbon filter, and give you more value down the road.
It looks to me like you are thinking of doing a DWC grow. Hydroponics is not easy, especially with a minimal gardening and/or cannabis background to start with. For a beginner it is most highly recommended that you use organic soil instead, until you get a feel for the plant and how it grows. By using organic soil you are going to save yourself money in the upfront costs (no need for expensive nutrients, pH meters and balancing solutions, or the pumps and buckets) and provide yourself with a much, much, easier grow system. Especially in that tiny little space, two DWC buckets would make two huge plants but the organics will grow at a pace that is a little more manageable for the area you have to work with. Start with extra plants, 6 total, so that the males can be removed and then keep the best looking 2 females to flower.
Use an organic potting soil and you are going to want to add some extra perlite to it. Some other items to purchase would be crushed dolomite lime, worm castings, MaxiCrop Sea kelp and/or dry kelp meal, compost (composted cow manure is good, but it HAS to be composted and not straight manure fertilizer). Do not select a soil with anything like moisture control or time release fertilizers. Miracle Grow is okay as long as you get the Organic Choice potting soil or one of the other Organic soils they have for flowers (although these require considerably more extra perlite to get the right aeration for indoor).
All together you could spend probably $25 on soil stuff but you're going to have a lot (like 5x more than you need) extra. The Compost, kelp, and the Worm castings can be used together in a 5 gallon bucket with a single pump and air stone to brew up some compost tea. This will provide a nutritional and microbe boost to your soil when they need a good pick me up. The dolomite used at 1 teaspoon per gallon of soil and mixed right in will help provide some calcium and magnesium as well as help buffer the pH of your mix to a healthy range for organics.
Hydro is going to be a headache. It is expensive but when it is done right... It does offer the best yields day for day. The choice is yours but do some research before making your mind up on this matter. Get all the other parts first.Grow Lights, Grow Bulbs and Hydroponics - Plantlighting Hydroponics & Grow LightseHydroponics.com - The Most Trusted Name in HydroponicsHydroponic Systems - Hydroponics, Advanced Nutrients, Grow Lights, and all the supplies for your home garden and grow room needs.
These are the hydroponic sites that I frequent. They don't carry everything, even between the three of them. If you need something special then eastwesthydro.com or greeners.com might carry it. Between these 5 sites, most of them have a lowest price guarantee, you will get the best deal available on the net from a reputable company. I suggest Ehydroponics personally, they tend to be timely, have good customer service, and have a great stock of items. I actually find their shipping charges tend to justify their slightly higher base costs, especially when putting together a couple of heavy items that other sites will charge you a arm and a leg for.