Simple: If you love them both go with the Polks and save yourself $160. I'm guessing your installer gets a commission on the more expensive speakers he's recommending. They may be very fine speakers but again, if your ears tell you they're both equally good...
In audio there is not necessarily a direct correlation between the amount spent and the quality obtained -- especially in speakers. There are big-bucks speakers that can be equaled or bested by others costing only a fraction of their price.
