Umm, given your very strong commitment to WAV over any form of compression (see other thread below), this is wild to me that you would choose either (a) connecting a USB directly to your core, or (b) using a toslink from an Apple endpoint. Not trying to challenge your commitment to WAV, just inferring from it that you have a strong commitment to the bits getting to your DAC as you desire them to be.
Given that, I’d personally counsel you to invest in a streamer commensurate with the rest of your chain. That could be a Ropieee, a Pi2AES, a BlueNote, A Lumin, or any of many many many others. You could choose to work with WiFi or Ethernet to make the connection back to your ROCK - WiFi won’t have any sonic consequences so long as you don’t have dropouts. But neither of your current approaches sits right with the rest of your chain. This is not like the analog domain where there’s an argument for “fewer devices”. I’m not sure what the rest of your chain is (though I’d love to know if you’d be willing to share), but either way you’re doing a fairly grave injustice to your music chain through either (a) or (b). They might be adequate to some, but I’m not buying it makes sense for you. You should have a very good plan A.
Happy to help you figure out which flavor is right. But where you’re headed I’m fairly confident is not right for you based on what I’ve learned about your preferences elsewhere.