Ryzen 7 3700X / 3800X paired with Ryzen 9 3900X
Ryzen 7 3700X / 3800X paired with Ryzen 9 3900X
then @OP, if they end up costing about the same either way, I think you could go with the 3700x with a game, because it would only be 10 dollars more. Or you could wait for Zen 3 and see what it provides.
It seems you're confirming the accuracy. Your main choice was 3700x, but seeing the 3800x for just 25€ more made you think it could be worth it.
It doesn't seem so. If the 3700x and the 3600x both cost around the same later, it makes sense to pick the 3700x.
You're asking for the most cost-effective option. Going up to 3800x instead of 3700x offers no real advantage, but you could invest the 25 if it delivers value.