The asus is the same card as the Zoltrix Pro 6.
The Asus site says
The A7N8X uses an onboard RealtekĀ® ALC650 audio CODEC A different chip - don't think it does bit accurate s/pdif transfers but it doesn't sound like that's your problem anyways. If it was actually sampling at 48k and you were only feeding it at 44.1, I think you'd have lots of zeros in there. If it sounds fast, my guess it that it's actually 44.1k file with a 48k wave header.
Open it up in something like Cool Edit Pro that shows you the sampling rate. If it says 48k, change the rate to 44.1
Note -
don't resample it, just change the sampling rate (it should be an instantaneous change - no processing required). If your computer starts working away, stop it...you want the other kind of change.
david