Damien,
No. A signal-to-noise ratio of "only" 100 dB is spectacularly good compared to the typical SNR found in analog gear-- about 60 dB for the best vinyl (most vinyl is much worse), a bit more for analog tape. There would be no audible advantage to moving from your current sound card to one with a greater than 100 dB S/N ratio.
Keep in mind that a noise floor that's -80 dB is totally inaudible with musical programming of any sort. Empirical tests that introduce distortion at increasing levels with the music have shown that the distortion is often not detected by trained listeners until the background distortion levels are increased to -40 dB to -30dB below the music signals.
Regards,
Alan
