Generally, if you set the fan to exhaust and blow the air out of the hood, you're fan isn't going to last very long. The salt air does a number on metal parts - especially all the copper in electrical motors. I added another 32W light to my nanocube, and added a 60mm fan blowing into the tank. I've just about doubled my evaporation rate, so in a nano it's still very manageable. I have my lights and fan on a powerstrip that is connected to a timer, so the fan turns on when the lights do in the morning, and they all turn off in the evening.
You may want to start with just one fan. My 1 fan more than handles the load of the extra light adds right now. Perhaps in the summer i might have to add another, but it only takes a few minutes.
BTW - i like your avatar. i can't wait for 4/2.