ASUS A7N8X Audio problems..!

I just got my new mobo Asus a7v8x (-deluxe), but I'm having problems with the audio outputs!
It has the two extra outputs named Cntr/sub and sur.
But when i plug in my 5.1 speakers (Cambridge Soundworks DTT2200) with 3 inputs the Center/sub channel is very weak/subdued (!?), if i plug in one of the other channels in there (cntr/sub channel), those speakers (one that "becomes" the center speaker and the other speaker "becomes" the sub) work fine.
If I plug the cntr/sub channel into the Mic. input and check the option for that in the nforce control panel it works fine!? I know the speakers are OK because i've tested them on a sblive 5.1 card and there they also work just fine!
Is this a hardware problem ie. should i return the mobo, or could there be a bios fix for this comming up?

Any ideas would be helpfull!

System:
WinXP SP1
Asus A7n8x
XP 2200+
512mb Corsair pc3200 CL2
Radeon 9000 128mb
2 adaptec scsi cards (one for internal and one for external)
HD:
Seagate ata100 80gb + Fujitsu 10gb ata66

That's not a knife... THIS is a knife!