That seems to be the way mine works (I can't be positive, as I have only tested it by forwarding to myself).
In Mail: Preferences:
I have the following setup:
Composing Tab: Replying:
Both "Use the same message format as the original" and "Quote the text of the original message" are unchecked
Under: When quoting text in forwards:
"Include all of the original message" is unchecked, while "Include selected text, if any, otherwise include all" is checked.
I'm attempting to test it by sending to an unrelated account. So far, all new text appears above quoted text. If that is fine, then I will attempt an automatic fwd by address and check again.
[update]The message sent to another account displayed as expected: ie with new text above the forwarded message.