I'd say there won't be much of a difference between the analog and digital connectors, but I don't have much to back it up.
But, I do know that it is likely you aren't using those connectors. In fact, most audio today is sent thru the IDE channels as opposed to the sound connectors. If you go to device manager and select "digital only" for your cd/dvd-roms, you will be using the IDE channels. Thus for volume you would not use CD-ROM/Auxillary/etc.. but wave I think (sorry on Linux right now, so I can't check for Windows).
Hope that helps.