IMO....
Without getting into headroom, oversampling, interpolation and all that sort of stuff I don't think there would be too much to gain.
Given that normal audio CDs only have 16 bits of resolution, I don't see how it would be any better. If you are using your SP/DIF card then you are probably already using a pretty high end D/A converter which means upsampling and converting to 24 bits wouldn't help too much since the original information was only 44.1kHz / 16 bits.
If you're talking about these new 24bit 96kHz "super" audio CDs as sources then that's a different story and it might be justified.
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Christian
#40104192 120Gb (no longer in my E36 M3, won't fit the E46 M3)