What is my best option for adding a second GPU?

Hi all, first post on L1 so apologies if it’s in the wrong subforum.

I have a mATX PC with a single 5060Ti, and I’d like to add a second one. My intended use is for local LLM inference with a single model split over two GPUs. I’ve been exploring as many options as I can but keep running into roadblocks.

Here are my limitations:

• Another GPU won’t fit in the case, nor into the second 16x slot of the motherboard.
• My mobo, Asus TUF-GAMING B550M Plus, only has a single PCI-E 4.0 16x slot, which doesn’t support 8x/8x bifurcation in the BIOS*. The second 16x slot is 3.0, on chipset lanes, and I’ve ruled that out for bandwidth/latency reasons with LLM model splitting.
• The mobo has a PCI-E 4.0 4x M.2 NVME slot on CPU lanes, but apparently the 5060ti doesn’t work well with m2 to pci-e extenders like ADT-Link’s K43SG because of … retiming issues? Given that the 5060ti is actually an 8x card with a 16x connector. [1] [2]
• Have a 550W Corsair PSU and Ryzen 5600X CPU at stock clocks/voltage. Happy to power-limit the GPU/s to 150W if that makes ‘em fit within the PSU’s operating capacity, or add a second PSU (eg Dell DA2).
• Trying to do this in a budget friendly way!

I’d love some advice on what my best options are. Buy a new mobo and case? Try to do something with Oculink instead? Consider a different GPU? Any other routes I haven’t considered?

Thanks everyone.

• The Asus manual says the PCI16X_1 slot “Support PCIe bifurcation for RAID on CPU function.” implying that you can run 4 m2 SSDs into the main 16x slot with a 4x/4x/4x/4x splitter card. I can’t tell if that would work with an M2 to PCI-E splitter of some kind.