Looking for some streaming advice

I am looking for some help in meeting some objectives whilst updating my streaming system please.

my current set up is fairly simple:

music source:  my CD collection ripped using Apple lossless to a Windows 10 PC which sits upstairs next to my router (BT Hub) running LMS and also iTunes.  I also stream a lot of radio (music and talk) and also use BBC Sounds to listen to archive stuff.  I also Spotify to audition music before I buy although once Spotify launch their lossless service I’ll probably stop buying music.

the network is both WiFi using the BT hub and a wired Ubiquiti AP.  The connection to my streamer is via a Devolo 500 power line.

my system is a Naim superuniti, a Logitech squeezebox touch and a pair of PMC twenty5 24’s.  I use iPeng to control the system.  I use the Touch as streamer rather than the superuniti so I can use iPeng.

I also use a Sonos 1 in the kitchen and a Logitech squeezebox radio in the dining room.  Both on WiFi

i use iTunes to keep all my music library on my iPhone (compressed) so I can listen in the car.

What I’m trying to achieve:

Overcome network issues where sometimes music stutters or hangs.  Also PC restarting and not restarting the LMS.

a single iPhone app that will seamlessly play music on all devices (currently the touch and radio are well integrated but not the Sonos.

improve SQ

what I’m considering 

Adding a Innuous Zenith Mark 3 connected (USB) directly to Superuniti with all my ripped music either moved or duplicated from PC to Zenith.  - this will presumably cure any network issues and should improve SQ.  I did consider a QNAP but purely for aesthetics discounted that option.

subscribing to Roon to unify all my needs

upgrading the Logitech Radio to a Naim Mu-so QB - improved SQ

Questions

1. Does this sound sensible / will it work?

2 how do I keep music on the Zenith and my PC in sync so that I can keep my phone updated with any new CD’s I rip.?

3. Is there any advantage in adding an Ethernet switch between the Zennith and Naim?