New to HiFi, need digital advice.

I am not an audiophile but I recently acquired a really nice high end system for free. (AR LS16 preamp, Madrigal Proceed HPA2 amp, Arcam CD92 CD player, Aerial Acoustics 7B tower speakers.  I have been learning as much as I can over the last week since I got it.

Now I'm trying to figure out how to put together a decent but not necessarily high end digital input system for as little money as possible.

So here is my plan. I know it is not high end and probably not commensurate with my system but hopefully will meet my needs:

Old iMac using iTunes to manage flac or alac files plugged into Schiit Modi 2 via USB cable and then into preamp via USB cable. I can us Apple's remote app on my iPhone to select/play music remotely (Works great).

Does this sound reasonable? If so it will only cost me about $100 for the Schiit DAC and $25 for a decent set of RCA cables (already purchased) and whatever I might need to spend on the USB cable. Anything I should know about the USB cable for this?

Thanks for the advice and apologies for my ignorance in all of this.

George