the guitar port does not override your sound card because the guitar port is not a sound card.it just runs through it
in the sound menu in the control pannel make sure your original sound card is on your pefered device.
the guitar port should show up as another recording device in your recording software.
wether the  M-Audiophile would produce better quality recordings ....hmm
not too shure of that depends on what card you have in now and that the sound is created within the software so it might be as good as it gets.