Streamer

+3 Cxn v2, with modwright tube dac and upgraded power supply. 

The streamer I have in my office system, a Pro-Ject Stream Box S2 Ultra, has usb out for a dac, accepts usb in from an external hard drive and, of course, has an ethernet connection.  Sounds great to me and comes in at just under $1k.  Good luck with your search.

So, on this topic. I have recently been looking at the A Capella III Streamer from 

Musica Pristina.

Does anyone have experience with them and/or this Streamer? It's a bit pricey, but it has direct I2S out, which is something I've been looking for.

Just a bit of cautionary advice: I2S interfaces are not always compatible between different manufacturers as the standard is relatively loosely defined

Yep, understand that fully. I am already using a Matrix Audio X-SPDIF 2. And my DAC is the PSAudio DSD, so I can validate whether a particular vendor supports that particular LVDS pinout. Luckily, the DSD DAC is a 'sort of' standard.