these 3 strings, available as singles can make an old instrument, braced for steel strings sound great while dropping the tension on the neck and top. the gauge required no nut slot modifications as well.
While not inexpensive, they wear like iron and the tone remains true for a long time. Used with a couple of wound silk and steel strings, Martin 0-18t just rings and is just as loud as another 0-18t with light gauge steel.