This question has been asked several times before. My answer is that the 390S upgrade is a no-brainer for anyone who owns a 39. I agree with the comments that described the sound of the 390S as "more liquid", or "smoother" than the 39. I like to say more "continuous".
BTW, I own a 39 which I had upgraded to a 390S a few months back.
Craig Zastera
BTW, I own a 39 which I had upgraded to a 390S a few months back.
Craig Zastera