Upgrades for the 220 Pro

[Graziano]

Having the 220 Pro with my Audiovector Si3 Avantgarde Arrete, what type of small upgrades can I do around the amplifier? 

Have anyone done some upgrades with
- Power cords or maybe any power isolation like Audioquest Niagara or Ansuz?
- Another dac or streamer?
- Feets under the 220 Pro?


I have:
Homemade power cord
Speakers cables Nordost Heimdall
Sonic design feets placed under the 220 pro
Streaming Tidal from Bluesound Node 2i

I also thinking about to buy one more 220 to get an 440 pro, it seems to be a good upgrade. 

Thank's a lot for some advices, if anyone done some upgrades that improves the sound for the 220 Pro