Playing MP3's on 2nd Soundcard

Question

Recently I tried to write a little app which I want to use to play MP3-Files. It was no Problem to use the predefined classes in the Microsoft.DirectX.AudioVideoPlayback namespace. Again, it wasn't a Problem to write my own classes to access different devices (I use two soundcards...) and play WAV-Files with classes from within the Microsoft.DirectX.DirectSound namespace (using classes like Microsoft.DirectX.DirectSound.Device or Microsoft.DirectX.DirectSound.SecondaryBuffer). BUT: How the hell do I write a class, that can play MP3's and uses my special Hardware? It just didn't work for MP3's because the Buffer Class does not accept them! I just want to be able to play two files at the same time on two different soundcards... Can this problem be that big??? Any suggestions?