I always liked the 160 AAC in iTunes, to me it sound's alot better than the 128 AAC default that my sister encodes her music at. I didn't notice a huge difference between 160 and 192 to warrent going higher. Best advice would be to rip your favorite song at like 128, 160, and 192 (or higher if you like) and see which sounds best to your ear, vs acceptable file size(if that is even an issue for you). Thats what I did originally and it let me work out which type was most acceptable for sound/size wise.