I have an opportunity to purchase either a pair of Polk Audio SDA SRS 2 (blade/blade) speakers or a pair of SDA SRS 3.1 TL speakers. Both are in good shape. Sellers are both asking around $500 for either set. If I buy one of these, they will primarily be used with a 2 channel stereo setup. Given that the price and condition of both are equal, which version of the SDA SRS would you recommend? I've never owned a pair. These would be replacing either my Polk R.T.A. 12 or Polk Model 11 speakers.