Need helpful recommendations for next two purchases

So I'm 73 just getting back into two-channel. So far I've purchased from Adrian ( great guy highly recommended) on Audiogon a pair of Canton 9k reference speakers with stands, and a Jamo c80 sub, and fancy speaker cables Wooo the hook has been set lol.  Oh and thanks again for the Canton feedback.  The Cantons are powered by my 30 yr old Adcom gfa555 250 watts per, Emotiva  XDA-1 preamp/DAC (24 bit/192 kHz), And a new Marantz CD 6006. The Marantz has a USB port which is set up for an iPhone, it also has a headphone amp and a DAC that can drive the amp directly. 
I know jack about streaming but believe it should be my next component. My question given the level of my system and a budget of about $600 what should I be considering for a streamer or whatever it is called to listen to music through Roon or other similar sources from the WWW?
 It seems the one's I've looked at are all Preamp/DAC/Streamers such as CambridgeCXN V2 ( way over budget) Marantz NA6006 and Bluestone Node2i both in budget.The problem is all three seem to be duplicating what my Emotiva already brings in the way of a preamp/DAC so why should I spend $$ for stuff I have already except if one is better then the Emotiva at preamping and DACing   OR are there just streamers I could buy please show me the way. Oh while I like detail the above system could use just a little warmth it is not bright or forward almost just right. Almost ... I see it coming lol it is always going to be almost.

An extra credit Help question I will post a bit down the road but you  could get me researching now what to replace my Adcom GFA 555 ( quiet as a mouse nothing leaking or bulging inside but its 30 years old) and at 73 I know what age can do that you can't see.
My budget is $2000+- I don't mind used but can't afford to by a Krell, McCormick, Bryston etc. and then get hammered with another couple of grand in repairs. Did I mention I'm retired on a fixed income, Scottish with a dear wife that I want her to remain so.  Oh while I like tubes at some level  I'm not a tube guy can't afford the upkeep or temptation to roll tubes. My shortlist to be researched beyond just their names include: a few pieces of Schiits,  XTZ A 300 or 2 biamped, Emotiva base X a 300 or 2 bi amped or Emotiva stealth PA1 biamped. I worry that Emotiva amps will add to much brightness forward sound. Also looking into a built kit from Akitika, Rotel RB1552 mk2, Optoma NuForce STA200,Nu Prime st10. At this point, these are just names do you like any? Do you have any other amps  I should consider given my set up noted above?
The room 12x16 vaulted ceiling 8 ft to about 18 ft system out 2 ft from the  8 ft wall.  WW carpet, 2 overstuffed chairs on either side of speakers.  lots of hanging plants ( in corners) three big glass windows behind my system, one glass sliding door to deck comprises one short wall,the other short wall has 8 ft opening,  behind my couch that faces the system is a wall with a big glass picture  2x3 ft. that long wall facing the system has plants in each corner and hanging baskets in each corner. Not a lot of echo despite all the glass life's a compromise. Thank you for reading all this stuff and for your kind recommendations. Be safe stay healthy listen to music.