This might also help & be more specific to your question: http://www.m4a.com/ (it is an oldish article!) An m4a encoded at 320 I've yet to see. It will sure be good quality. The one advantage m4a has over mp3 is the size. It's a format that's still in its growing stages as far as popularity goes. Before mp3 what was there? mp2! When mp3 1st came out there wasn't that many players with the ability to play it. Wow how things have changed! There's now portable players with the ability to play m4a (no I'm not just talking about iPod.) Perhaps if you search the forum you might find out more.