[Max Lobovsky]

I am still unsure of what you are trying to record, so this may not apply. The "best" way to do it would be to record each source independently then mix them later in an audio editing program (I assume Audacity is one). This especially makes sense because it sounds like some of your sources are already digital (CD, MP3) and it would make no sense to play them back into a mixer then redigitze them. You will have better quality and more freedom to tweak the sound after the fact instead of trying to get it right at the time.