I have used D'Addario strings now for years. Every now and again I get convinced by other guitarists to try another brand (Ernie Ball, Martin, Fender, Roto Sound etc) but none provide me with the same tone as these boys do.
The Phosphor Bronze wound strings for acoustic guitar have a clear but mellow tone to them. The may be cheap but don't be put off by the price (they're a damn sight more expensive in off line music stores).
They have a clear bottom end and not to bright top end, but give a lovely deep, rich mellow sound and are easy to play.
I would choose D'Addarios every time and Ive yet to find a guitar string to better them - even the more expensive ones dont do it for me.