Hey martinman, you and I seem to have similar priced setups at the moment. I believe I may have some insight for you. My system is as follows:
B&W CM9 S2
Peachtree Nova 300
Jamo sub
iFi Zen Stream + Roon (Qobuz & Tidal) with USB out
I've experimented with networking and power stuff--and I'm going to experiment with DAC's next--but for me, the big level up was moving to the iFi streamer. I wrote a little review with some thoughts, which you can read here on Agon. Some of the only other things that could compete with the level of improvement were adding a sub, adding nicer feet to the speakers/stands, and placing the speakers on stands.