Hlep chosing a streamer/server for my DAC

I'm still leaning Innuos. 

Nothing wrong with that, you will be happy. 

I favor the Lumin U2, not only for its ability to stream great music, but for its optical ethernet connection as well (optical ethernet could by the wave of the future).

Option number 2. 

Aurender has been a stalwart in the digital realm for years. You Aurender guys are pretty loyal bunch, no doubt for a very good reason. I haven't been thinking about that streamer because it's my understanding that all are not Roon capable except for one. Maybe Roon is not such a necessary thing?

Aurender users don't think so. Option number 3. 

I'd be interested all of your opinions on Roon. I have read some who say it improves the sound, some say it degrades it. What do you guys think? 

Roon is wonderful, it sounds incredible and they continually make improvements which changes the sound, usually for the better. Is Squeeze (Innuos sense is based on Squeeze and therefore almost equivalent) on my streamer (option number 4) better? On many tracks yes, but that doesn't make Roon inferior, just different. I still use Roon 90% of the time as the user interface is world class. I have discovered many new artists and wonderful music I never knew existed. Once you get a streamer that is Roon capable there is a trial period. Oh, and don't go to the Roon forum and ask the question regarding sound quality as the "bits are bits" flat-earthers will shoot you down and ask for "evidence". 

I'm still unclear which is the best connection from streamer to DAC. Is it USB, AES, I2S, etc.? I would be interested in your experience with that aspect of digital streaming.

You are looking for absolutes, there usually are none in audio. Each manufacturer has their own ideas and implement their own philosophies and therefore each unit will have its own optimal connection method, which then varies on the receiving unit connected to it. Same goes for the software on each player. 

You guys are the best, Eric

We know. 

You have received some great suggestions.  However, before you start making some hardware purchases, I suggest that you give audirvana and qobuz a try with your macbook. I recently purchased a mac mini and installed audirvana on it streaming qobuz and tidal and roon to my Sony Oled TV and Martin Logan motion vision soundbar with SVS subwoofer and was truly amazed at how great audirvana and qobuz sounded (to my ear better than roon). Now, it is not at the level of Linear Audio Tube aero dacs with ray reserve tubes and aurender streamers in a sophisticated headphone system or over the top speaker system with ancillary wywires platinum and cardas clear cabling  — getting audiophile level reproduction can be a lengthy process requiring hefty expenditures and a fair amount of effort in getting the system you want.

You should be able to run Audirvāna from a MacBook. Audirvāna is fully compatible with macOS 

• macOS 10.13 (High Sierra) or later

• At least 4GB of RAM (8GB recommended for optimal performance)

If you plan to use the Audirvāna Remote app to control playback from another device, the Remote app itself requires macOS 11.0 or later and an Apple M1 chip or newer for Mac, or iOS 12.0 or later for iPhone/iPad.

Both audirvana and qobuz have a nice free trial period.

Audirvana — 30 day

Qobuz — 60 days offer in May 2025, I believe.

Have fun.

I have an Innuos Zen Mk. 3 I’m very happy with (paired with PS Audio Directstream DAC). The Sense app is very good. Prior to this I used a stripped down, music-only Mac Mini M2 with Audirvāna, which is pretty darn good and quite a bargain setup, but there was always some glitch happening so I got the Innuos.

I use a McIntosh streamer using an iPhone to access Roon.

Cambridge Audio EXN 100 will handle your DSD requirements over usb.  It comes with its own internal ESS Sabre DAC but you could use your own.  If for some reason the streamer and DAC are incompatible then you could use the internal DAC , which is no slouch, as a fallback .  
  The app is an important part of the streaming experience.  CA Stream Magic isn’t perfect-I don’t think a perfect app exists- but it’s the best of the dozen or so that I’ve used.

  The EXN would be half your budget and leave you plenty to spend on those pricey DSD downloads.  It’s possible to get really great digital sound at a much lower price point than with analog