My system comprises by a CXA81 amp, lumin u1 mini transport, qnap file server (running minimserver) and monitor audio silver 500 speakers. I was using rpi4 with volumio and the upgrade to lumin resulted tremendous sound quality. I am thinking about replacing the DAC of CXA81 by a standalone DAC (RME adi 2 DAC, Denafrips Ares II, chord qutest or.....) but I do not know the difference to SQ. Would it be better purchasing a better amp than purchasing a DAC that costs 1.000-1.500 euro ?