Just a followup on my XLD True VBR setting. In the 3 years I have been encoding, I have yet to find a better setting for music. I have tested the 110 quality setting against everything from classical, rock, jazz, punk… everything I have thrown at it - it creates an amazing sounding AAC with all the room I expect from the AAC codec.
The range of the encodes are truly VBR and as such I find that the 110 setting, comes in under the AAC+ iTunes setting at higher quality. This is especially true for mono material as stated above which comes in at almost half of what iTunes encodes. Even when the 110 setting flares up to 319kbps, and it will if there is a particularly complicated piece of music, it still comes in under iTunes for the same material in most cases.
While I have come across a few posters who proclaim that the 110 setting is overkill and you could reduce the setting down to 90 (Around 190kbps), I like the piece of mind in knowing my music collection is basically transparent even on beefy sound systems. Oh and it holds up AMAZINGLY well against all output I have tried. While I could save a few MB here or there, not having to worry about the quality of my encodes is a bester trade-off to me.
So if you haven't given the XLD AAC 110 setting a shot, I doubt you will find anything better sounding for the file size.