system clock selection for cs43122/pcm1792/4/8 ?

[rlim]

The popular sigma-delta dacs these days offer a range of system clock frequencies - 128/192/256/384/512/768fs, and I am wondering if increasing the clock frequency would improve the sigma delta modulator performance. Or are they just operating their modulators at some fixed ratio of fs such that any higher system clock you put in will merely be divided down in the chip? Seems like if that's what they are doing, then selecting the lowest system clock frequency would be beneficial from an emi standpoint.....

Thanks,
Richard