Aurender A20 or Lumin X1

Both are great but as @ghdprentice stated, how they sound in your system and to your ears takes precedence over any of our opinions. Beyond that, look for features that are more important to you.

You asked for opinion, so here is mine. A quick glance at the features tells me A20 is a better product, especially the analog section, better proprietary app (unless you prefer ROON, which requires a separate computer to run ROON core). Critical Listening Mode, dedicated Headphone section and User-Installable Storage option which eliminates the need for external NAS. Aurender, IMHO offers the most elegant one-box solution.

I am not going to get into the debate of one box vs separates. Separates are to be pursued if you like flexibility and chasing ultimate SQ. Otherwise, one box offerings like A20 are pretty darn good to keep things simple and uncluttered.

Good advice on the separate components at that price level. I have an Aurender N200.    It's been great, keeps getting better with each firmware and software revision 

ROON is the only way I roll. I am definitely a power user of ROON. So no interest in Aurrender (I have heard it). I prefer a $400 cheap computer to run my ROON core in a far off room away from my 3 ROON Endpoints. I use fibre optic to make any negatives of using a $400 computer far away from my gear go away.

The X1 is a great streamer and I owned it. I like the DAC of the Schitt Yggi+ Less is More over the X1's DAC. The streamer on the X1 is great as is the LeedH volume control. There is a new Lumin streamer that takes the DAC section out and is cheaper. That would be what I would get if I went back to a Lumin streamer. The X1 DAC is very good but I like the Schitt more on the top end.

The Sonore OpticalRendu is as good as the streamer on the X1, but sounds different. A bit calmer over the wild child streamer sound of the X1.

The PlayBack Designs Streamer-IF is maybe my best streamer. Unlike the other 2 which used fibre I am using Ethernet and SPDIF for the PlayBack Designs streamer into a Benchmark DAC3B. That stream sounds great. The plan is to buy a PlayBack Designs Dream DAC to use the Plink of the Streamer-IF (so fibre). That Plink streamer is likely going to be the best I have ever had. It only works on Nagra and PlayBack Designs DACs.

The main question for you is ROON or no ROON.

Feature sets are usually bigger differences than SQ.

Do you want Roon or don’t want?

My first DAC was a Lumin D2 with an LPS.

The sound was very good, musical, detail, depth, I was very happy with SQ. Unfortunatly, the app was a problem. Connectivity, chashes, post upgrade lack of functionality and system recognition. Support via trouble tickets was less than ideal. 

I replaced it with an Aurrender N20 and since added a second to my home. Both are excellent pieces, SQ fantastic, tech support very good, IMO the best app of a pure streamer solution.