a, since i do not know you or your listening habits, i can only offer that i use a 20 watt ss class a amp in my livigroom. it is plenty for me in a 14 x 24 x 10 foot room. this is 3360 cubics and fairly large.
rob says they work well with his amp in his room and mitchell says no. he used the vsm's which are more efficient and room filling and he was in a smaller room. no one is going to be able to advise on this because it is very personal.
for as many that use 12 watts and say it is fine for them, there are people with 40 that say its too little.
good luck.
b