60 WPC sufficient power?

Do you know the efficiency rating of your speakers (I'd guess in the 86-88 db range)?

The question should be, is there a better 60 watt amp for my speakers out there? 60 watts is plenty period. A BEL 50 watt amp will blow the speakers apart without breaking a sweat. So will many other amps with high current. Also amps under the 100 watt range will almost allways sound better than the same co's higher output amps simply because lower watt amps are easier to make with less parts(output devices) daisy chained together to get more power. If you find yourself needing more than this 60-75 watt range, something is for sure wrong with either the speaker selection or mabe you live in a barn size house.

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.