My advice is, go listen to the a6, a6 master and a8 and chooce wisely. The a8 sounds the best digitally and anaologue. The a6 master is getting closer to a8 (with the upgrade lps psu). A6 sounds okay/good and analogue.
Reading you have decent r2r dac, wanting the smoothes sounds, you will prefer the a8 (but let your ears be the judge BUT a big BUT! Do that with decent enough headphones, or amp+speakers). Doing that you will notice the a8 sound more organic, but you have to experience it yourself to understand.
Because most will always say there is no difference, a zen stream will just sounds the same streaming as a 8000 euro streaming device… (which is not true but you’ll get my point
). Let your own ears be the judge