320 is overkill in any format. Try MP3 lame alt standard preset. That will do jusice to your iems. With 320 all you'll have are overly large files and worse battery life. Congrats on the Shures
I just bought the Shure Ec2s for my ipod and I was wondering if it would be worth it to change my music to 320 kps? My music is currently at 128kps. would I see a good difference?