Burning iTunes Plus and other 256 bit rate material to get best quality?

Question

I understand that iTunes Plus and most songs on Amazon are provided at a higher bit rate than non-Plus iTunes songs in order to provide higher audio quality on playback. But, does this quality differential come through when burning a song to disc from within iTunes?
I ask because of an experiment I just conducted. I downloaded the same song from iTunes (not a Plus version) and from Amazon. The Amazon version takes up twice as much file space as the iTunes version. (The ACC file at 128kbps was 5MB while the MPEG file at 256 kbps was 11.6MB.) However, when I burned both songs to a CD, those files where identical in size. Further, when played on a near-audiophile stereo system, I could hear no discernible difference between the two.
So the question: Does whatever extra information and hence sound quality contained in the Plus or other 256 kbps material get lost in the conversion to audio CD format? Are there settings in iTunes I'm missing? Are there alternative software or file formats available that would burn audio CDs without this loss?
(I realize that whatever difference there is in sound quality would not be detectable on most equipment. What I'm looking for is to preserve quality differences that can be heard on high-end equipment. As it is, I'm able to tell the difference between well-recorded and produced commercial CDs and the same material bought through iTunes.)

Answer 1

The quality of compressed audio is not always linked to file size. I believe it is possible for a 128 kbps AAC file to sound as good as a 256 kbps MP3 file. MP3 is not the best audio compression format but it is by far the most commonplace. A 128 kbps AAC file isn't as good as a 192 kbps AAC file, however.
When your audio files were uncompressed for burning to audio CD they naturally became the same size because there no longer was any compression.
If your objective is to have audio CDs that sound best on high-end equipment then you should continue buying audio CDs rather than purchasing on-line music. That way there is no loss in audio quality from compression. I'm not aware of a source that is selling lossless on-line music downloads.