What else have you got running there? Playing Killing Me Softly, the cpu usage on my clapped out work computer running an ancient Core i5 hovered around 15% and rarely above 20%. This wasn't via a USB connection however.

Main system - Sources (Kodi-HTPC, Vero 4k, FireTV, Sat) into Trinnov Altitude 32 (8-16) (+Roon), Trinnov Amplitude 8 amp & Vivid Audio (Giya G3, V1.5) and REL Stentor III speakers. Others: F80 + Raspberry Pi and other Pi systems.