DAC upgrade

Don’t ruin a system like that adding room correction dsp.  Those devices degrade the signal quality greatly. Never heard one that didn’t. However if you did use REW and fixed your room acoustics that would be amazing. 
as far as dacs go, PLAYBACK MPD-8 seems to be the new go to for analog like sound with reference grade dimensionality.  Another option would be to try a Grimm mu2 which would potentially allow you to sell the Aurender. EMM labs has also been stirring the pot lately. I meet a lot of people buying used gear online and have talked to some fine seasoned high end audiophiles. One with similar tastes to me and has tried pretty much everything said his EMM labs DAC will never leave his side. There’s also the denafrips terminator + 15th. I’ve tried a lot of dacs and the terminator has been one of the most natural sounding and capable dacs. I had the esoteric N01XD SE and it was probably the most real and realistic sounding of the bunch but ultimately found it to be kind of bland musically.  In that price range I can’t offer much more than that unfortunately but might be something in there of value. Also you said you have great interconnects. May I ask what you’re using and if you have good power cords too?

I went from a Rockna Wavedream to a Lector s192 tube based dac. Couldn’t be further apart as far as comparing quality dacs are concerned. Rockna is super accurate with a strong attack. Saw deep into the recordings. Very real sounding. The Lector is very smooth and liquid. Connect with the music differently with both. With the Lector I just listen. The Rockna I tended to analyze the music more. Perhaps not quite as relaxing for me personally. I wouldn’t say that’s a negative for the Rockna and I would gladly own one again. I was selling equipment and was able to swap dacs and took the opportunity. I got to hear my system with each dac prior to having to decide. Wish I could own both. 
‘I’ve owned the Topping dl90, Cambridge cxn modified by ModWright with tubes and Audio Note dacs as well. The Rockna and Lector are at another level. The AN was unique and enjoyable as well. Good luck

Thank you all so much. 
as for interconnects, have Bordost Odin 2 for power cords to the M400 amps, Audioquest Dragon to streamer and preamp, Valhalla 2 to DAVE, Odin 1 xlr preamp to amps, Siltech between DAC and preamp, Valhalla 2 Ethernet with Nordost qnet with fiber interposed and Valhalla 2 bnc streamer to DAC. 

+1 on the Audio Mirror DACs.  Just recently acquired the Tubadour VI and it's sublime!  I look forward to it breaking in and sounding even better.  Very natural and musical DAC.  I would seriously consider contacting Vlad as he's the sweetest guy you'll ever come across.  I can only imagine how his flagship Wave DAC sounds.  It's within your budget and there's one at a steal of a used price on USAM now.  

Take a look into Vitus DACs, which are known for sounding warm. Might be a great match for your system. I own the Masterpiece DAC and am very happy.