Best route for audio

Hi,
I have recently ripped all my CD's on to an external hard drive and use a brilliant free programme , MediaMonkey, to organise and play them.
At the moment I use the headphone outlet of one of two PC's I own. This means that I am listening via the sound card and there is an audible difference in the sound quality between the two PC's. I presume this is due to different quality of the sound cards and other audio related circuitry.
Because I am enjoying listening to my music so much more now that it is so easily accessible I have ordered a digital to analogue converter with USB port and headphone outlet so that I can bypass the sound card which at the moment is the weak link in my set up.
My question is will it then matter which of the two PC's I use as my intermediary between the external hard drive and the digital to analogue converter or being that the signal sent from the PC is digital then will the quality be uniform between the two PC's ?
Regards Alex