I tried the playfi app with an Arcam streamer a few years ago and couldn't believe how bad it was, clunky not intuitive at all and kept freezing. The Arcam sounded great but I sold it on after about a month because of the god awful app. Best avoided, Bluesound and Sonos have the most stable apps
Id stick with your Naim and use a streamer. Honestly the node 2i in my experience is very very good for the money even without adding an external dac. The app is very good as well. Many many audiophiles with nice kit use them...
Monitor Audio, Kef and Dali all go very well with the Nad C320BEE in my experience. Also the Marantz PM6000 series amps are not an upgrade for your Nad which in my opinion is the best cheap integrated money can buy
A Pure iPod dock which won rave reviews at the time and did sound prettg good however, the remote control for it used to inexplicably switch my tv on and off.... ridiculous
Most expensive was my Roksan Oxygene amp/cd combo which retailed at around £7k and the amp buzzed and sounded flat and...
Ground-breaking for a music obsessive like me was discovering Spotify, it was jaw dropping to be able to access just about everything I'd ever want to listen to......
I've since moved to Tidal because Spotify sucks sound wise but whew what a game changer...
My Vincent SV 236. Why? It's like beauty and the beast sound-wise, huge depth and punch but also has finesse at all volumes. Also, it enhances every source I put through it and can drive any speaker I've used so far. It's an end game amp for me.