It depends on the situation.
When somebody gives you an opinion and you say "sounds good",
then you just say.
좋아 / 좋아요 - good
그래 좋아/ 네 좋습니다 - Ok, good.
When somebody introduce you a good music or sth and you say "sounds good"
then it is like
이 노래 좋네 / 이 노래 좋네요 - this song is good.
듣기 좋다 / 듣기 좋습니다 - it is good listen to.
hope it helps