I don't know if it uses the same opamps and DACs, I haven't looked, however it does do a better job processing. Most people's complains about the Audigy's aren't related to DACs, it's the DSP that's the problem. Like I said, all sound is resampled to 48kHz, so if you play a CD it gets resampled. Well that resampling isn't great, it's not bad, but it's not great, it introduces an aliasing reflection that degrades sound.
The X-Fi, regardless of the make, fixes that problem. In Games and Entertainment mode does resample all sound, but does so using an extremely high quality algorithm that adds basically no distortion (resampling doesn't have to degrade sound quality, it just does if it's bad). Also it has a new Audio Creation mode where it doesn't do resampling.
Thus the major problem with Audigy 2 sound quality has been fixed.
I haven't done any blind side-by-side comparisons of the cards you want in 2-channel mode so I can't help you, but I can say that the X-Fi sounds very good in 2-channel mode.