Not sure if you're answering your own question or not with the comment you made above about the DAC breaking in "harshness arose .... seems to become less." - might want to contact W4S and see what they say about the breakin experience and possibly how their DAC "reacts" with the source you are feeding it with.
Do think, if nothing else, that you are short changing yourself in what music your are probably "not hearing or isn't being revealed" using the radioshack ICs and whatever comparable SCs you are using, as well as the quality of the cable between the "source" and the DAC.
Do think, if nothing else, that you are short changing yourself in what music your are probably "not hearing or isn't being revealed" using the radioshack ICs and whatever comparable SCs you are using, as well as the quality of the cable between the "source" and the DAC.