Mail.app : Improved dock count

I recently began trying out Mail.app after using Thunderbird for quite a while. Still on the fence if I want to switch (the main reason i might is that it has better iCal support).

Anyway my problem... can I change the dock to display in the red circle the number of NEW unread emails? I normally have quite a few unread emails in my inbox, but only want it to show up with a count when there are new ones. This is what thunderbird did and it was a nice unobtrusive way of knowing I have new mails. Not keen on the whole Growl throwing up boxes all over my screen to tell me I have mail scene.

Thanks for your help.