I started out with a set of five & I noticed improved detail and a higher soundstage. The one negative was that I noticed some inner ear pressure with some songs. The second set eliminated that pressure & gave me a more spacious sound. I installed an additional 5 following the instructions with the FEQ and the sound quality was kicked up another notch. My audiophile friends noticed the improvement as well. My room is fairly well damped with wall to wall carpeting, drapes and 1 inch thick Tectum panels with 6 inches of open batt fiberglass behind them on the back wall and half the ceiling so I was surprised to hear the difference. Both demonstrations I saw were in sonically live rooms but the system worked in my room and was worth the expense.