Can't answer your question directly but might put a finer point on it.
According to the specs, the Monitor Audio S8's will produce 91 dB of sound at 1 meter given 1 watt. At 60 watts the sound pressure would be about 109 dB at 1m. At 2m (6.6 ft) it should produce 105 dB. At 3m (9.9 ft) it will produce about 102 dB. This sounds barely adequate depending on your room size, seating distance, the type of music you play, and how loud you listen. Moreover, the Adcom will be maxed out. So the question is, how well does the Adcom perform near its peak power rating?
The S8 is rated to handle 175 watts. I would be tempted to borrow a higher power amplifier to see if there was an improvement.