http://growershouse.com/air-water-co2?c2c_brand=8099&cat=158
Take a look at those, they are the best bang for your buck. The 4" would probably work but the 6" would be best and is adjustable. Also the most efficient fan cfm for the wattage only 35w on the 6"315cfm. Thats the one i recommend and you could probably dial it down, and when you decide to get something a little more powerful that t5s you can still use this fan.