Hi Mike
Regarding creative cards, you are mixing voices and polyphony up. (Easily done with the creative (Ouch) marketing used)
The Polyphony of Creative cards vary between 32 and 128 notes, depending on the type of card. (The average is 64)
The 512 voices you refer to are the number of sounds (Voices) they can access, later software updates allowed the cards to access the computer ram, thus increasing the number of sounds (Voices) that could be accessed. (These can be identified in the small print which states that the additional number of sounds (voices) is dependent on the computer system used)
Hope this makes things clearer.

Bill