Ah ... freeware Cocoa apps. There's more and more of these things every week. Found a link on Apple discussions about
AACelerator. Quoth the readme:
How to Use AACelerator
To start, drag and drop a selection of audio files from the Finder or an audio CD onto the AACelerator application icon. AACelerator will display the name of each audio file in a table the main window. Once you have all of the desired audio files loaded, select the desired encoding rate from the pop-up menu. AAC audio can be encoded at data rates from 16 kilobits per second (kbps) all the way up to 256 kbps.
Now I have to get the 6Pro! Someone who has 6Pro please check this and report? With the proper settings entered into QT, iTunes will play them. I just don't know what the space saving will come to.