as best as i can understand it the problem is with the tags and not with amarok
Qt/KDE uses utf-8 internally so nothing utf8 can confuse it.
however only id3v2.4 uses utf8 properly
you can use utf16 and it should work.
the problem with the windows tags must be the first byte still says it's latin1.
there must be some way to set it right
you could try running this on them
java -jar id3conv.jar song.mp3
java also uses utf8 internally just like KDE
if you have id3v2.4 you can try
to convert them
i think you would use
eyeD3 --force-update --set-encoding=utf8 song.mp3
might need more command switches -- not sure