Please help

i don't think that you would gain very much sound quality from going to hdmi cable for connecting audio from pc to stereo . i think your problem is the source of music from your pc. if you are streaming or playing media in compressed format i would think that could be the cause . cd quality sound is about 44100 samples per a second , windows media player default setting is about 30000 +/- . so windows media player's default quality is 30% lower than cd quality . there is a setting to improve this . most people would think , how come i didn't notice this on the computer speakers , well they are lower powered , lower resolution . so connect the headphone out to your stereo again and play a cd in the cd drive and see what you get , maybe play the same cd in you stereo's cd player to compare . if the volume is still low check your settings and sound card configuration . but more or less you should be able to get a bout the same overall quality playing a cd on a computer as you would a cd player , as for digital media it will vary based on the compression rate and the quality of the digital media .