If you do that, you'll be bypassing the headunit.
You want Sound Card -> Headunit AUX IN -> Amplifier(s)
You already asked that. Yes, you could, but you would be bypassing the headunit, and losing all of its functionality, including the radio.could i conect the radio to my sound car integrated in the pc(the green slot) and conect the sound card usb via the usb port to my amplifiers?
SOUND CARD -> HEADUNIT AUX IN -> AMPLIFIER(S)
It doesn't matter for a car environment. You're not going to be using 7.1 from the sound card.i have a sound car audigy usb....it is suposed to my 7.1 but i dont see 8 ports.... i'm i suposed to use 'y' rca?
You'll use simple stereo (left & right channels) into the headunit.