A:Answer It really depends on how loud you listen. The Bose 901 Series 1 Owners Guide states "The 901 can be used with any high quality amplifier. Its efficiency enables operation with moderately powered amplifiers, yet it can be used with the highest powered amplifiers to reproduce undistorted orchestral peaks at high volume levels." However, the older Bose 901's were less efficient and needed more power to listen at loud levels than the newer vented models. Early Bose 901s were of an acoustic suspension design which requires more power all else being equal than the vented designs. The equalization curve in the newer models were also less severe, requiring less power from the amp to get deep bass.