Which server / renderer to buy?

I use a 4TB Antipodes DX as my ripper/server connected via USB or SPDIF to my Esoteric K-01X ("Kay") as a DAC.  I still prefer SACD on my Kay so she gives me the flexability to spin the silver from time to time (old habits) and the Antipodes gives me the convenience of a server as well as Tidal accessiblity.  The DAC section on Kay is every bit of impressive as her transport capability.  In short, both the Esoteric and Antipodes are outstanding and they make wonderful music together.  I've heard many other combos and tried a few different DAC's but none surpassing this combo.

Thank you all for the awesome advice.  I have a lot to chew on here and, I guess I could waste some money or not.  Maybe I'll wimp out and just upgrade my turntable...;-).  Again, thanks, PeteG.

USB and the USB interface in a computer was never intended for audio use or hi speed networking. Recognition of and elimination of Jitter was not a design consideration for USB specifications and applications, just transferring bits and bytes.

USB was basically adapted as an inexpensive way to connect multiple peripherals such as back-up drives, personal printers, software transfer or loading etc.. for personal computers. It replaced slow and often unreliable serial interfaces.   One of the engineers who helped developed USB and has amongst the best USB audio devices on the market, has now turned to Ethernet as a sonically superior interface. Accuphase, that arguably make hi resolution SACD/CD players and DACs of the highest echelon both sonically and engineering-wise, has always used an Ethernet derived HS or HS Link2 between their digital gear. Linn have always used Ethernet. I believe that I2S is a version of Ethernet used by PS Audio and others. Now Bryston is on the bandwagon I think. 

If you are going to use USB as a music storage medium for highest quality it can achieve, the best way to do this is via USB stick loaded from your PC or whatever. Load it, plug it into the front of your player and turn off the write function since all you are doing is reads. I find that you can have mixes or different genres on a stick. If you read the 1/18 HFN/RR one of the more engineering savvy writers (Keith Howard) makes this same point. Use your USB drive from your NAS or computer as a backup. You can read more about the implementation of USB here. They have all the goodies people fret over with SSDs and HDDs for music playback.

https://www.mouser.com/applications/usb-flash-drives-myths-dispelled/

All other things being equal the best (audio) connections use Ethernet. As we found when we were developing thinwire Ethernet (there were three computer/semiconductor companies involved) the most significant determining factor is the quality of the ethernet adaptor and a properly made cable of the correct category. As the other person said, use a crossover cable to hook up your source to your "player." For purest playback, try to avoid a switch. But they are convenient, especially if you want to download DXD files for playback or streaming. Consider that if Ethernet connections are implemented properly they have no jitter of their own. You don't need to buy "magic bugs" to plug into your USB ports, etc. to remove noise or jitter.

Yes they (Ethernet and USB sticks) measure better and sound better if you have a transparent system. IMHIO.