Digital streaming options for my system are confusing

Bluesound Node 2 or 2i is an excellent choice.  Wireless connection with simple setup provided in the BluOS app.  Use your phone or tablet for control.  Link for Tidal subscription is in the BluOS app.  You also get for free, Radio Paradise and hundreds of internet radio stations.

Connection to your Mac can be rca from the Node to an input on the Mac or if you want to try the internal dac in the Mac a digital cable is required between Node and Mac.  Both can be connected at the same time so you can toggle inputs on the Mac to see if you prefer the Nodes internal dac or the one in your Mac.

 I have the Node 2i and am very much impressed with it.

I'll add my +1 for the node2i. As an old guy it was very easy to setup wireless. 

You can do much better than a Node.

The Node is an excellent device for a starter system but with an amplifier of your quality the Node is not going to offer the best sound quality.

The Node does offer a lot for its price including a great app, and many different music streaming service options.

The issue with the Node is that it is an inexpensive device designed to offer good performance with mostly midfi gear.

The best choice would be a Innuous server these range from $1,400.00 devices up to much more expensive servers at $2,500-4k

The Innuous is very easy to setup and does require a Roon subscription which is $120 a year or $500 lifetime.

Roon itself is amazing the experience it offers is top notch it is easy to use and integrates perfectly with Tidal as Tidal is a partner.

If you have CD’s you can also rip them to the system and access them that way.

Sound quality of the Innuous gear is fantastic, custom built motherboards, custom designed USB card, and quiet power supplies.

The Innuous has a USB output which the Node doesn’t have and through Roon you can upconvert a 16 bit 44k digital stream into a psedo high res stream at 24 bit 192k up to 32 bit 384k and above.

In this way you can dramatically improve the digital sound of your system this is something the Node can’t do.

The Innuous gear is very easy to setup in less than 5mins you are running and streaming Tidal.

Dave and Troy
Audio Doctor NJ Node and Innuous dealers

If the 6700 has a USB input it is likely an early version that if I remember correctly was limited to 24/96 max so the innuous is probably overkill on that amp.
Could be totally wrong of course but my McIntosh with built in DAC that looks very similar input wise to the 6700 was limited to 24/96.