In his Positive Feedback review, Dave Clark recommends the 512 setting. In my own experience, this setting sounds good on virtually all redbook discs. In truth, however, I have switched back in forth endlessly between all of the settings and I am yet to hear more than very subtle changes in performance.
Read the Positive Feedback review and then play with the settings. You can make the changes "on the fly" with the Cary remote control. Perhaps your ears are more refined than my own and you may just hear something significant. If you do, please report back!
The Positive Feedback review also addresses the break-in period and states that 500 - 600 hours of play seems to be appropriate. (WOW!)
As to "break in" in my own system, I have had my 306 SACD for about 4 months and I am surprised almost every day because the unit just seems to get better and better. I would guess that I must have somewhere between 4 and 5 hundred hours on the player. It does get better, the more you play it. This player is phenomenal!
I've owned, and listened to, a bunch of very fine CD & SACD players. the Cary definitely holds its own against any of the competition. I actually sold the highly touted Ayre C5Xe player and kept the Cary because I felt that ultimately, the Cary sounded more "real" in my system.
I think that the areas where the Cary 306 SACD really shines are imaging, soundstaging, dynamics, bass performance, and an uncanny ability to project the sound of voices and instruments with lifelike realism, suspended in space against totally black background.
SACD and Redbook performance is superb with the Cary 306 SACD.