First let me start out by saying that I know that the UH-4 is a amp/dac combo. That said, I don't know enough about how to read the specs of each unit to make an informed decision. Looking at the summary's they both have digital volume control, bass boost
( C5 +6.5db@ 80 Hz) ( UH-4 2x gain select). The UH-4 has a X feed w/bypass. The UH-4 list( 16bit/48kHz dig audio, I assume thats
the dac). The C5 has a feq. response of +/- of 0.02 db were as the UH-4 feq. response is 13 Hz to 22.5 kHz +0/1 db.
Output impedance for the C5 is 2.2 ohms, the UH-4 OP impedance is 0.4 ohms.
This were the C5 Specs start to list max output in ohms Vs. VRMS. 600 ohms @ 4.146 VRMS 150 ohms @ 3.337 VRMS, 32 Ohms
@ 1.010VRMS. The C5 lists THD + N as 20-20 Hz at 150 ohms 0.0009%, 32 ohms at 45%.