i just bought a new computer with an asus motherboard (a7n8x-e deluxe) and tossed in my old creative sb live! 5.1 card. the motherboard has built in audio (nvidia nforce 2 chipset) is the quality better with the built-in? or is it the same? im using the creative card with the kx drivers (using the center/sub as a headphone) so the nasty hiss you get out of the front (green) out is gone. does the nvidia have the same front hiss problem? the headphones i use are sony mdrcd-380s. any help is appreciated.

There is no easy answer as a pc system is a very complex with various factors to take into account, but there is an easy digestion, i guess you already knew what i'm going to say: Listen!
If you're serious about this you could ask a friend to swap the cable for you so you won't know which source it is and then try to spot a difference. and that result won't be a generic answer aswell, just for you, your ears and your setup, everything can be broken and is more often than expected. And, no I'm not giving in in the easy 'you're listening to pop rock so it won't make a difference anyway'... I guess none of the people here can give you a more generic answer.

I had the same hissing problem with my Soundblaster Live. I fixed it by going into Volume settings and muting the cd-player option. The soundcard was connected to my DVD drive causing the noises made by the DVD drive to bleed through to the soundcard.
I also found that the latest drivers on the Creative site significantly improved the sound quality. Furthermore, I suggest that you download the latest nvidia nforce chipset drivers, 6.53 at nvidia.com. Also, www.nforcershq.com have the best drivers for your SoundStorm sound card.

I hope that of some assistance.