"The Chasam Sofer's lifespan extended from the Sha'agas Aryeh and the Noda B'Yehudah, whom he knew in his youth, to Rav Samson Raphael Hirsch, whose Horeb he admired." (Chasam Sofer, Commentary on the Torah, Artscroll, p. xvi)
"Rav Yisroel (Salanter) had a great longing to become acquainted with Rabbi Hirsch and to learn his views on the means needed to consolidate traditional Jewry in Russia. He had great respect for the regenerator of German Jewry, and no one else was more deeply convinced of the desperate need of Russian Jewry for such a personality." Rabbi Naftoli Hertz Ehrmann, who arranged a meeting between these two giants in 1876 in Berlin. (2 Giants Speak, p. 6)
Rav Baruch Ber Leibowitz had such awe for R' Yisroel Salanter, who he knew from Kovno, that he would tremble whenever his name was mentioned. (from Artscroll bio on Rav Baruch Ber).