I recently bought 2 sets of Polk SDA2s from different sources. One pair has 1 tweeter, 2 mids & the bass radiator. The 2nd pair has 2 tweeters, 3 mids & the bass radiator. BOTH pairs are marked on the back SDA2. Did Polk use the extra drivers in the 2nd pair of SDA2s for the cancellation signal sent by the special cable? The pair with the extra drivers seems to sound better. I plan to keep one pair & sell the other (out of room!). Which one would be better to keep. Thanks for any response!