The next step to a better system

For streaming consider the Bluesound Node 2 and a subscription to Tidal HiFi with uncompressed cd quality streams.  You can use the onboard DAC for starters or connect to a DAC of your choosing.

 On the analog front, I would say your cartridge may be interesting to upgrade. It seems your phono preamp can handle a moving coil cartridge, so perhaps a nice step up in that department would be very worthwhile.  I highly recommend the Lyra Delos.

I like the idea of the cambridge 851D and the similar Sony, but I feel constrained by such a unit.  I like the idea of a separate DAC and a separate streamer or small computer.  For now I use a mac mini and external HD to stream to my PS Audio DAC.  I am using Tidal hifi as well as my own ripped CD collection all controlled by Roon, which I adore.  Who knows, in the future, I may opt for a streamer such as an auralic or a blue sound instead of the mac mini.  I think that the ability to change the streaming style and software is nice to keep independent from the DAC.  In my case, I may want to change the streaming part and keep the same DAC or vice versa, and at different times.  All that said, that seems like a killer deal on the 851D that you found!  Almost too good to pass up, and just try on for size.  It will be challenging to find a quality DAC and decent streamer that cheap. (though possible I guess with a used Bluesound Node version 1 and a used, reasonably priced DAC).