ogg is pretty close to AAC. I think it's MP4, right? Generally, I find that AAC is the same as MP3 LAME one notch up, and two notches on Frauenhofer. So Frauenhofer MP3 320 is the same as LAME 256 or AAC/Ogg 192. All of those are transparent in 99.9% of music. In my library, I've gone one notch into overkill... AAC 256. I added VBR so the file would be distributed intelligently.