It's a good idea to read the interview of the developers of ATRAC3+ to understand a little more about the theory. I think 128kbps ATRAC3+ is noticeably better than 132kbps ATRAC3, and even a 96kbps rate in ATRAC3+ is acceptable in many cases. Once below 96kbps, too much is missing from the music for me, even in ATRAC3+.