When you download what you call a cdg file, you mean mp3+g right?
If that's the case, all you need is any editing software like WaveLab or the Creative WaveStudio to convert (decode) the compressed audio (mp3) to wave so this way you have a wave+g file all ready to be converted to bin and burned to create your real cdg disk!!
Also, why not normalise the track while it's a wave track?
It might look complicated but a good editing software will be able to decode the entire folder to wave so all you need to do is relaxed!
It's my understanding that MTU is working on something to convert from the mp3+g & cdg to KMA???