just want to jump in on the mod debate . . .
the only thing we can really do with the Xtreme Musics and Fatal1ty cards (and the Xtreme Gamer as well), is reduce the amount of noise, and increase the clarity of the output - by replacing or removing capacitors and the OPAMPs.
The actual dynamic range that the card is capable of playing back at, and the THD+N quality is entirelly dependant upon the DAC on the card. Being able to check these capabilites through loop-back testing will run into a wall with the ADC on the card as well; meaning, even if the DAC is capable of 115db DR output, but the ADC is only capable of 103db DR input, loop-back testing will only show 103db DR in testing; and most card specs are based on loop-back testing by the manufacturer.
But, even still, the small variations between many of the DACs chosen on the higher end cards level very negligible changes that are extremelly hard to notice . . . especially in the case of 8 channel DACs.
All the PCB components, though, play a big part in the actual clarity of the playback, and the amount of distortion and noise one might experience. Capacitor choice, OPAMP choice, even VRM choice as well - whether they decided to include an EMI shield or not, also. Component degradation will play a big role in audio playback over time, and in the case where mediocre PCB components have been chosen by the manufacturer, playback quality a year after install will not be the same as when the card was brand new.