Assume both are outputting a perfectly flat eq curve and both are going to the same speakers which one would sound better, My friend wants to buy my car PC system instead of getting a Empeg player which he assumes will be dying soon because of the age.
Hard numbers would be nice (I have checked the FAQ) and it gives frequency responce numbers for the aux input but none of the empeg output.

Based on both being EQ'd properly, they would sound indistinguishable from each other.

The empeg is better in about a thousand ways that have nothing to do with the sound quality.

I have often wondered why the frquiency responce for the empeg wasn't listed anywhere, I like my empeg but I can't just tell my friend its better "because" because is not an answer anyone have real hard facts I can tell him. the soundcard he wants to use has these numbers

Audio Performance

Signal-to-Noise Ratio with AES17 filter (A-Weighted)
2V Rated Output 1V Rated Output
Stereo Output 108dB 102dB
Front and Rear Channels 108dB 102dB
Center, Subwoofer and Rear Center 108dB 102dB

Total Harmonic Distortion + Noise at 1kHz (AES17) = 0.004% (1V, 2V Rated Output)
Frequency Response (+/-3dB, 24-bit/96kHz input ) = <10Hz to 46kHz (1V, 2V Rated Output)

Quote:
Based on both being EQ'd properly, they would sound indistinguishable from each other.

The empeg is better in about a thousand ways that have nothing to do with the sound quality.

The Audigy 2 NX sports a Sigmatel STAC9460S DAC.
http://www.sigmatel.com/documents/stac9460-pb-1-0.pdf
Along with handy stuff like 192kHz/24bit support (though not both at the same time on that particular card), it looks like a better unit all-around than the integrated Phillips widget in the empeg.
In a car, though, I seriously doubt that the difference would be audible, and the empeg is better in a number of other ways.

On the other hand, a serious car PC could include things like professional audio cards (RME Hammerfall or Lynx), real-time convolution (BruteFIR, DRC, etc.), support for more advanced audio containers, CUE sheets, etc.
Getting that pile of parts to be as usable as an empeg would be a significant amount of work, however.. and explains why I have an empeg and not a car PC.

I do toy with the idea of getting a 12V-modded version of this on and off, though, and feeding it with the Eutronix digital output that's available for the empeg. Best of both worlds
http://www.deqx.com/dsp-product/PDC26P-Preamp.html