What front end piece should I upgrade?

About a year ago, I wrote this group about a problem I was having with limited bass (only when using a streamer fed PS Audio DS Jr DAC compared to an Oppo 105 player) as well as some harshness and sibilance (much worse on the Oppo than DS Jr) that was leading to fatigue . I am using a Small Green Computer (SGC) i5 as a NAS and Roon renderer and a Sonore ultraRendu with linear transformer as the streamer and Roon endpoint.  I stream Quobuz as well as have ALAC files stored on the SSD in the SGC - do not notice much difference between the ALAC files and Quobuz.  The ethernet cables are Pangea Premier SE and I am not using any special switch - just relying on my Netgear router.  An Audioquest Carbon USB cable takes the Roon endpoint signal to the DS Jr.  I found the SQ of the Bridge Roon endpoint on the DAC to be noisy and not as good as using the Sonore product  Finally, I have a Sim Audio Moon 600i Integrated and the speakers are SF Sonetto V (both 1st generation).

When I wrote in before, Soix and others suggested that I replace my bi-wire Kimber 4TC speaker cables with something like AZ Satori as well as my Monster M1500 XLR interconnects between the DS Jr. with AZ  Crystal Matrix Reference.  I switched the speaker cables to AZ Satori bi-wire and immediately found somewhat improved bass (much more noticeable on the Oppo than PS Audio) but with no change to the harshness.  Since I have an RCA set of AZ Matrix that I was running from my Oppo 105 to the integrated, I A/B both sets of interconnects through the DS Jr and found the Monsters indistinguishable.  So I did not change them. 

While I can significantly improve the bass out of the DS Jr. by adjusting the Roon DSP equalization, (+2db from 30-100 hz with a sharp roll off below 25 hz), as soon as I add the DSP, there is a noticeable worsening of the midrange harshness and sibilance.  I have found reducing upper midrange and high frequencies to try to eliminate the harshness to cause “blandness." A subwoofer is not an option (bride of 45 years) and room acoustics, if anything, would be considered more dead than live / bright.

Some options I have considered are:

1.  Try HQ Player instead of Roon DSP, however there is still some harshness even when I don't engage DSP.  I know I can try this for free but I am not that computer savy, worry that I will not interface HQ Player accurately and also wonder whether the i5 SGC can handle it. 

2.  Add another link in the streamer chain such as a SmoothLan, optical Rendu, PS AirLens, or some other recommended solution.

3.  Replace the DS Jr. with something like a Lab 12, Line Magnetic, Canor Audio, Mojo / Merason or R2R or some other recommended solution (around $4K new or used). For some reason, I think the DAC is more of the problem than the streamer, but I may not be correct about that and open to suggestions. 

I hope I have provided adequate information and will appreciate any suggestions.  Thanks

Wow, that is quite the journey you have had. I would recommend moving from symptomatic solutions and go for the source of the problem. I think the best approach is to identify and install great components that sound great. Then play with cables and equalization to get the very most out of your system. This sounds like a component level problem. 

The problem is either the streamer or DAC. Neither of yours are over the top high quality units. Typically PS Audio equipment is not harsh or fatiguing. But then, the DAC is a very budget oriented DAC. The Line Magnetic DAC has a very good reputation and the sonic characteristics that would greatly improve the sound of your system. 

If that change does not fix the whole problem (extremely unlikely) then I would save up and invest in a Aurender streamer... used would be fine. Virtual any would be a very significant upgrade from what you are using now. 

These two changes, without the current problems you are having would be great upgrades to your system. 

I recently purchased a SIM Audio Moon 390D DAC and am very pleased with its characteristics. I raise the point as it sounds like you’re looking for improved lower frequency range and that’s exactly what I experienced with this DAC - a boost in low frequencies, and without any hint of mid/high frequency fatigue.

Used costs are in the order of $2000 (there’s a unit available on USAM now for which I have no affiliation), and I have no regrets with the purchased I made a couple of months ago (i.e., the honeymoon hasn't worn off!!!). 

I don’t recall the DS Jr. being regarded as a bright or harsh sounding DAC so may not be the source of the problem although there are some warmer sounding DACs some of which you mentioned.  I would try the SmoothLan first as it seems to help in taming harshness/removing glare and is obviously a lot cheaper than a new DAC, and I believe they offer a trial period so a low-risk option to try.