I installed a whole house fan in my previous house years ago.
Here's the company I purchased from http://www.grainger.com/Grainger/who...-8wb?op=search
Look for belt drive , ball bearing , 2 speed and timer .
That's what I bought and it was totally reliable.
Most times we'd turn it on high for an hour before bed , then low at bedtime ( fairly quiet) and set the timer as some times it would get to cool.
I used a 30" in a 1800sq ft home .
These fans move a lot of air ( A LOT ! ) so your duct size may be an issue here.
Another issue can be adequate ventilation in your attic , here's where a ridge vent can save the day.
Do you have enough volume in the attic so as to not create a wind tunnel.
If you have blown in insulation you don't want it blowing out your vents or plugging them.
Another thing to think about is how you plan on insulating them in the heating climate.
Gas water heater and possible back drafting , don't starve it for air.
Don't mean to throw a wet blanket just some things to be aware of .
We enjoyed the one we had .