The best way to test that is to take your 320 VBR MP3 and use WinAmp to decode it and write the results out as a WAV file. Now write this WAV file and the original WAV that the MP3 was created from onto an audio CD.

You can then compare both on the same hardware, e.g. the CD player in question.

And, if at all possible, get someone else to write the audio CD, and don't have them in the room while you're testing -- so you don't know until after making your mind up, which was the original and which the encoding.

Peter