Responding Amen to a Chazan Who Recites Kaddish Quietly

A chazan who recites the Kaddish very quietly, is it permissible to respond Amen and Yehei Shmei Rabbah louder than the one reciting?

One should not respond Amen louder than the one reciting, but Yehei Shmei Rabbah should be said loudly and even louder than the one reciting.

Talmud, Berachot, page 45a: "Rav Chanan bar Abba said: From where do we know that one who answers Amen should not raise his voice louder than the one reciting the blessing? As it is stated: 'Magnify the Lord with me, and let us exalt His name together.'" This is also ruled in Shulchan Aruch, Siman 124, paragraph 12. Some have written that this rule does not apply to Kaddish, but only to matters that fulfill an obligation. However, from the words of the Mishnah Berurah there, SK 47, it is evident that he holds that even regarding Kaddish, this rule applies, as he wrote that even in Baruchu, one should not raise their voice louder than the one reciting, and apparently Baruchu and Kaddish share the same rule. Nevertheless, Yehei Shmei Rabbah should be said loudly and even louder than the one reciting, as it is a separate matter and not a response to the words of the one saying Kaddish. As written in Mishnah Berurah, Siman 56, SK 2: "When the responder says Yehei Shmei Rabbah, he should pause slightly between Amen and Yehei Shmei Rabbah, and similarly between Amen and Modim, because the word Amen is a response to the shaliach tzibur, and Yehei Shmei Rabbah is a statement in its own right."