For a natural sound and "singer-song writers, both male and female. Lots of acoustic/piano", I would check out the Songer Audio S1X. Several people said the S1X was the most natural sounding speakers at Capital Audiofest.
Another option is the YG Hailey 3. You can get a used/demo Hailey 2 and send it to YG to be upgraded to the version 3. I've been listening to a lot of piano and neo classical since I got my Hailey's back from YG a month ago and they are excellent for piano and violin.