With the new Navi 21’s coming out, 68xx?XT or whatever and the RTX 2060, 70, 80, 90 you’ll need to see which gives the greatest hashrate per watt when tuned for max efficiency. Then take 80% or your breaker size in Europe, and buy the # of GPU’s who’s combined running wattage will fit into that without going over. Buy a power supply that is capable of 100% of the breaker size and you are set.
At $600 per GPU you may only be able to afford a 6 card rig but one that will max out the mining capability of your breaker. Hopefully you could get 8 cards but be sure to get the ones that have the highest hashrate per watt. I’m thinking it will be AMD’s newest Navi 21, we’ll see.
By the way, people are getting hashrates with 5700XT’s of over 500Kh/w. That’s a high value because most of us are in the 400’s. Should big navi get into the 600Kh/w range that would be terrific.
One power supply may not be enough especially at the voltage here in the states (120V) but even if you run two power supplies, stay under the max your breaker can handle and run at 80%.