Nucleus, is completely plug and play, ROON software add a lossless streaming service such as Quboz ROON will integrate any ripped or downloaded files.
Roon software includes multi-room capability and features parametric EQ .
REW and a microphone
The single largest improvement you can make is to acoustically measure your room with REW ( Room EQ Wizard ) software.
REW is comprehensive even without a microphone you can experiment with its 'room simulation' feature, it will create EQ filters for you which you can then load into ROON, or your RME dac or send straight to your Dutch&Dutch 8C loudspeakers.
Intona Hi-Speed USB isolator, if all else fails, Intona's isolator can save the day, it can't improve a properly engineered dac, but really poor designs do still exist.
Superb measurements, super sound quality,elegant design.
Just buy cable which is 'fit for purpose', I supply Mogami with all of our systems, it is quad core, heavily shielded, supple and I like the name.
Cable for life!
State of the art amplifiers and dacs are relatively expensive, the large gains in SQ are always to be found in loudspeakers and their interaction with the room.