Low audio output from rear ports on new P5WD2-E Premium bo..

I have just installed my new P5WD2-E Premium motherboard and have found
that the audio output levels from the rear ports are very, very low.

I have tried the latest Realtek driver ALC882M from the ASUS site,
version 5.10.0.5188 and have also tried the latest ALC882 driver from
the Realtek site, version 5.10.0.5273, dated 28 June 2006. I find the
same with both drivers. I also found it in Linux, so it MUST be the board.

With all volumes at high and all equalisations at full boost on all
frequencies, both in the Realtek HD Audio Manager and in whichever
media player I use, I can still only get very quiet audio levels from a
range of different passive pc speakers I have tried.
I have spent much time configuring the Realtek HD Audio Manager which I
now know inside-out and it cannot be improved anymore by tweaking the
settings.

Significantly, if I try using headphones on the front-panel audio output
of my Antec case (with the AAFC header set to Legacy AC'97 in the Bios)
I get much more volume from the front panel connection than if I try
the headphones on the rear panel socket having adjusted and
optimised the Realtek HD Audio Manager settings appropriately for the
headphones.

I am sure it is not the fault of the speakers themselves having tested
them on other computers. The result with the headphones strongly
suggests it cannot be a fault of the output device being driven.

Obviously I will only be using simple passive speakers in the
short-term, but that is not the point.

Is there something wrong with my board or is this normal for this board?

If it is normal, why does it happen? It is certainly not normal compared
with various other on-board 5.1 audio output motherboards (including
ASUS boards) which I have used (using the same sets of speakers!)

Can anyone help please?

Thanks
James