Good morning everyone, I have a pair of SDA SRS's I would like to bi-amp. I have a Adcom GFA-565 SE for the bottom end. I have several amps to choose for the highs. What I have to choose from is, Yamaha M-45, M-60, and M-70. A Sansui B 2102. Adcom GFA 545 ii. Heath AA 2500 and an Adcom GFA 1. The last time I bi-amped I used the Yamaha M-45 and M-60. It was ok for low volume but that was it. No mods to the speakers. Thanks for and input.