To be fair though, the 4090 and 5090 are much easier capable of saturating PCI express than the 3090 is, even at 4 lanes per card the 3090 rarely manages to saturate the links, it still handsomely pays off to split down to 4 lanes and add more cards.

I used:

https://c-payne.com/

Very high quality and manageable prices.

I've purchase 16 of these - cpayne is great! Hope he finds a US distributor to help with tariffs a bit!