I need some advice

For a streamer I’d recommend Innuos or Aurender for ease of use, reliability, sound quality, and customer support.  The Innuos Pulse is $3800 and the Aurender N200 is $6300.  For a DAC the Denafrips Pontus 15th is $2000 but I’d also get their Hermes DDC to go with it that would bring total cost to $3300, or you could go for their flagship Terminator 15th DAC for $6000.  Given your speakers I’d consider going with a tube preamp, and the Linear Tube Audio MicroZOTL and Spatial Audio Raven preamps are excellent with the former being a little more neutral and the latter with a little more tube warmth but still relatively neutral, and both are around $6000 and offer trial periods.  If you’re not open to tubes the Pass Labs XP-12 or Ayre KX-8 are around $6000 and well worth considering.  Any combination of these will drastically improve the overall performance of your system and excellent speakers IMHO. 

I’m not familiar with your amp, but if that’s something you’re looking to upgrade I’ll mention this used McCormack DNA 500 because if I had your speakers I’d be all over this for only $3500, and they don’t come up for sale often.  Read the reviews. 
https://www.usaudiomart.com/details/650201477-mccormack-dna-500/

 Anyway, just some ideas to ponder FWIW, and best of luck. 

At the price of the Mooon 891 I’d be looking at separates unless you’re extremely space constrained or really want the convenience of one box.  Being beholden to one manufacturer’s streamer, DAC, and preamp is a big commitment for three critical components.  I read one review that had high praise for the preamp and DAC but found the streamer a bit lacking by comparison, which points out the risk of putting all your eggs in one basket.  It is clear there’s room for huge improvement over what you have now, and if you share your budget and what improvements you’re looking for and what sound characteristics are most important to you you’ll get some good recommendations here.