I currently have the same setup and thought that a six inch fan would do the trick to keep my lights and it didn't do the job either with minimal ducting possible. Then I added a six inch booster fan and that only helped acouple degrees. After weeks of trial and error with ducting, moving the fan into different locations and messing around with my two intakes. Turns out the best thing to do was to buy a 100 dollar Ice Flow system with a water pump and a cooler. Its was the only way I can get the temps to drop from 90's to high 70's. It would've been easier to spend the money on LED's Have you ever thought about the Ive flow?