Considering an upgrade

@jaytor regarding a silent PC you could pick up something fanless like an Intel NUC for relatively low cost, and migrate your Roon Core onto that device. If you really like the Roon software.

I'd recommend checking out the user interface that you'd end up using with any other music management devices, if you're willing to replace the Roon Core. Besides the W4S and Innuos there is Aurender and Lumin (requires an external NAS).

But going with separates for the DAC and network streamer will open more options for a change (improvement) in your sound quality. Auditioning different DACs is what I'd recommend.

Thanks for the comments. I really like the Roon interface and have a lifetime subscription. I also have four Bluesound Node 2is that I use for other zones in my house, so I would like to stick with Roon. 

I've spent some time looking into the Innuos Zen Mk3 and it seems like a good value. For those that have used this as a Roon server and endpoint, does it have enough horsepower to handle a few zones (almost always playing the same music) and a little DSP work (such as a couple of parametric equalization filters)?

I have a couple of old Intel NUCs lying around from my business, so installing Roon ROCK on one of those might also be an option. Anyone have experience with this? 

I'm also interested in hearing about DAC recommendations in the <$6K range that would be noticeably better than the Yggy. Particularly in the smoothness of the midrange. The dealers in my local area don't seem to carry many of the "hot" DACs, so auditioning will probably require a purchase with return option, which I'm somewhat reluctant to do unless I feel there is a good chance that I'd keep it.

The three DACs that I've read a lot about that seem intriguing are the PS Audio DirectStream, the Lapizator Amber 3, and the Denafrips Terminator. 

I’d add the Metrum Pavane Level 3 DAC to your list. It’s also an R2R DAC like the Yggy, but the Pavane is a non-oversampling design that generally tends to sound smoother and more “analog” like, which sounds like it may appeal to you. I believe Hifi Heaven offers a purchase and return option, and it might well be worth considering if you haven’t yet heard a NOS DAC. People who love them, LOVE them.  FWIW, and best of luck.

Some people consider the Yggdrasil to be one of the absolute best DACs available, so recommendations really depends on what you personally might consider a noticeable improvement. Two of the three DACs you listed are in a different direction than the Yggdrasil, in my opinion. But is that why you thought they might be good options to audition? It's hard to know what "smoothness of the midrange" means exactly.

For what it's worth, these are the DACs we carry and recommend that are also within your budget: Lumin, RME, Prism Sound, Bryston, Devialet. Plus our own Neko Audio D100 Mk2. For R2R, I'd suggest looking at Soekris. If you want something with built-in room correction, there's the Trinnov ST2-HiFi.

@nekoaudio - I don't have much experience auditioning different DACs. I've heard a few other systems, but the only DACs I've had extensive time with in the past ten years is the Levinson No 39, W4S DAC-2, and my Yggy. I had owned the No 39 since the mid 90s when I started to get into computer audio. At the time, I was using a USB to SPDIF converter which wasn't very reliable, so I bought the W4S. Unfortunately, I found that I liked the sound of the No 39 more, even though it was 15 years old. A couple years later, I bought the Yggy based on all the positive reviews, and liked it much better than the other two. 

My interest in the three DACs is based on other's comments and reviews. I have not heard any of them. I'm curious about your comments regarding a different direction than the Yggy. Can you elaborate?

Thanks,