When you get iTunes Match, all music that is matched from your iTunes library is available at 256
AAC. That's an upgrade for your older 128 AAC tracks, but a downgrade from lossless tracks. Normally this will only affect the music on the iPad or other iOS devices, but it may be possible (so I understand) to sync these higher quality tracks back to your iTunes library.
The only mention I can remember of 320 MP3 was in a cloud music comparison. I think it was
Amazon or Google that was using it for the songs your purchase through them.
Let me see if I can find that article. . .
Well, I can't find the exact article I remember, but there are a ton of them. If you are curious just do a Google search for 'cloud music comparison'; but set aside a couple hours if you are going to read them all (though I suspect the repetition after the first couple will discourage all but the hardiest of fact finders). It was Google who offers the 320 MP3 tracks, btw.
Lots of info on iTunes Match in this thread, if you missed it. Especially the last 10 or so posts.
http://www.ipadforums.net/new-membe...assistance/53636-itunes-match-launched-5.html