Thanks a lot
@OCC7N and
@sajunky for all your clarifications!
When you go up from R-1 NOS. You also get more information in the songs, the music is not only more relaxing, but at the same time also "tiring" because there is soo many information in just one note being played or a word from a singer.
It is not information like resolution you would find in a deltasigma. It is more concentrated with more weight/density.
It is important that the source has a good power solution, even though it is HE models, it can easily collapse: sound too dark/veiled or mushy as some has reported. With a good source the sound is more saturated, which makes it life-like.
DI20HE is a very good addition to take the sound further. It opens up more and makes the bass notes sweeter.
I could say go all in, but I rather recommend you start low so you know where you are heading.
R28NOS and DI24HE. This combo should be hard to beat. Youtube videos of the mk2 is pretty positive, and if the NOS model is an upgrade. I rather risk 1150/28NOS dollars on a DAC than 2390/27RE dollars on R27RE. The DDC will probably be a keeper no matter what DAC you get because of what it does to the music.
Do I think the R28NOS and DI24HE would equal or maybe beat the 27RE. Yes. It will not replace or enhance to the same black level maybe, but still achieve same level enjoyment. The R27RE can not beat what the DI20HE does*. I assume the 24HE even takes this further, I have no experience with the 24HE, but I know 90% what the DI20HE does.
*None of the Audio-gd DACs can do what the DI20HE does. It is the missing link.