The halachic importance of answering Amen can not be minimized. The folks at Halachipedia compiled a number of sources to inform us:
Chazal viewed the recitation of Amen very highly. In fact, Chazal tell us that responding Amen is of greater significance than reciting the Beracha. The failure to recite Amen is considered a gross transgression, while responding Amen with great concentration opens the gates of Gan Eden.
In addition to the man-to-God aspect in the answering of Amen, I’d like to discuss a man-to-man aspect.
When you’re davening from the Amud, it’s very lonely, except for the imaginary man on your right shoulder telling you to go faster, and the one on your left insisting that you slow down. Unfortunately neither of those voices provides much comfort. But when you hear the Tzibbur collectively answer Amen, you feel that something tangible has been accomplished with your brocha, or with your Kaddish.
This goes beyond the great z’chus for a deceased relative if you’re an Aval. When the Tzibbur answers Amen to each Brocha, we are bringing awareness of Hashem and His presence into the world. And that’s the reason why we we’re davening, in fact that’s the reason we were created. What could be better than that?
One of the wonderful things about my morning minyan of about 30 daveners, is the fact that we have a very high Amen rate. I would say it’s 90% or higher. When you hear that chorus, each brocha takes on a new meaning. You feel transformed from a sometimes-less-than-perfect reader, to a catalyst for collective spiritual growth. And that’s something that can really make your morning.
There’s tremendous power in the Amen. If you haven’t been motivated by the Chazals on the subject, please think about the tremendous chesed your are doing for the Baal Tefillah, as you make it clear that he’s not just today’s daily reader, rather he is a part of an important service to God.