Secondly, even if you did want to process at 96kHz, you'd have plenty of CPU left to do so. It's only 2x as intensive as 48kHz (this is a 32 bit CPU so using 16 bit vs 32 bit math is mostly the same, sans DSP instructions) and that amount of headroom is likely available, for example: https://www.rockbox.org/wiki/CodecPerformanceComparison
Thirdly, the article you linked talks about high end DACs but says nothing about the DSP on the card, other than that it has one, for doing... something (?)
Firstly, getting from uncompressed at the input to compressed is basic processing.
Seriously, you don't. Non risk instructions often take Multiple cycles, so you can only do a tiny number of them between samples, usually just enough to compress it to fit the bus speed without loss.
https://en.m.wikipedia.org/wiki/Cycles_per_instruction
Secondly, even if you did want to process at 96kHz, you'd have plenty of CPU left to do so. It's only 2x as intensive as 48kHz (this is a 32 bit CPU so using 16 bit vs 32 bit math is mostly the same, sans DSP instructions) and that amount of headroom is likely available, for example: https://www.rockbox.org/wiki/CodecPerformanceComparison
Thirdly, the article you linked talks about high end DACs but says nothing about the DSP on the card, other than that it has one, for doing... something (?)