There is something very wrong here. Cakewalks meters should be dancing away as Mr Argo says when you play back. That is independant of whatever soundcard you have. And on top of that you have bass distortion on midi playback?
It appears there is a fault somewhere in your midi playback loop, I just don't understand how midi plays back and yet you cannot see the meters moving. They are enabled okay? Right click on the meter and select 60db from the list of options. You wont see cakewalks meters moving on mp3 or wav playback unless they are loaded into cakewalk, so a CD wont move the meters either.
But is GS midi enabled? I thought it could play back audio only? Its either that or something isn't right in your Aureal midi set-up. There has to be a simple explanation here.
Midi is different to mp3 and wav, it is a set of "instructions" to whatever is your midi device to play a certain note at a certain velocity for a certain amount of time......you get the picture. So it is your selected midi device that supplies the "sound". And as its not playing correctly, it could be that is where your problems lie.