Choice of Onkyo M-501 power amp @ 150 watts or Yamaha M-45 @125 watts. My HT: Receiver - Onkyo TX-DS787, mains - Polk RTI10b, center-Polk CSI5, surronds - Polk FXI5, sub - Velodyne CHT120 and Sony & Onkyo CD. Also Samsung Blu-Ray DVD. Using Monster Cable Z Series. Any suggestion would be greatly appreciated. Thanks. Want to BI-AMP system.