What would be the next upgrade point from R630/R730 v4 CPUs in order to, say, half idle power usage? - eviltoast

I have few machines and am wondering when to start bothering with upgrades. Power is not too expensive here so I would probably switch if I can halve the idle wattage whenever more recent used hardware hits the second hand market.

I am currently looking at 70-90W per server.

NAS server has 4 disks 1 ram stick, proxmox has 8 disks full ram.

Alternatively, do I ride with the current setup until they fall apart?