Dynaco made an amp called the MkIII that was a 60 watt monoblock. This turned out to be a good amount of power for the original Advent. You can still buy the MkIII as a kit (looks like this is for one channel):
http://www.triodeelectronics.com/trmk3tuampki.html
http://www.triodeelectronics.com/trmk3tuampki.html