Sorry for not posting sooner. Winamp doesn't really convert files, there is a special output plugin that writes the sound it generates while playing the music to a wav file. Go to options -> preferences -> output, select Disk Writer. I also took a look at your files you uploaded. there are some missing files. the mini2fs needs the sound bank files with all the instruments and stuff. it should have come with the set as a .smap and .2sflib
I'm not sure about youtube videos, but the music from winamp sounds exactly like the music from the game. I even did a test and played the song on both winamp and my ds, no differences I could hear at all.