According to this:
http://en.wikipedia.org/wiki/Adaptive_T ... tic_Coding
"In the recently released Sonic Stage version 3.2 and 3.3 some more bitrates have been introduced, the available bitrates are: 48, 64, 96, 128, 160, 192, 256, 320 and 352 kbit/s. The newer bitrates are not always compatible with all older hardware decoders, however, some of the older hardware has been found to be compatible with certain newer ATRAC3plus bitrates."
All you should need is an update.
Here is a rooty tooty for Soundstage:
http://www.pspcrazy.com/index.php?page= ... icle&id=43
I know Soundforge 9 will do what you want. I have used Goldwave in the past but version 5.22 does not seem to have Atrac3 capability anymore.
I don't know how much this helps.