Camac seems to have the most room in the upper register. The Aoyama “Princess Sakura” has lower-than-usual string tension, and I have a 1912 L&H with very low string tension and lever gut strings. It has a beautiful, full, rich sound. Definitely not tinny or weak.
Carl Swanson builds extra space into his upper register if you are able to find a used Swanson pedal harp. His semi-guilded Empire has always been my favorite harp.