Yes, I think I inadvertently underweighted the part where you said you have Cat5E in the walls.

5 ports of 2.5GBASE-T is $100 to $130 at the moment. 2.5GBASE NICs are pretty cheap and available, but 2.5 was never used in enterprise, so there's no secondhand gear that really supports it -- you're buying all new.

Newish 10GBASE-T should also support 2.5GBASE-T and 5GBASE-T, but check to make sure. This 802.3bz is usually called "multigigabit" as shorthand. Macs support multigigabit, and so do most of the newer or better SFP+ transceivers. There are some secondhand 10GBASE-T NICs around, but you'd probably end up buying new, because not many were used in enterprises.

I guess it either boils down to getting the 10GBASE-T switch and mixed NICs, or paying less and getting the 2.5GBASE-T switch and 2.5 NICs for now. Just think about what you plan to do with it over the next three years or so. I will say that I don't think it's a waste to go 2.5GBASE-T and saving 75%, even if you change your mind eventually.

I got a TrendNet 5 port 2.5Gb swith for $99 from Amazon.

https://www.amazon.com/dp/B08XWK4HNT?ref=ppx_yo2ov_dt_b_product_details&th=1

I just upgraded my connection between my Windows gaming/workstation box and my Unraid box with This Trendnet 5 port 2.5Gb switch today. I also updated to the latest RC build to make sure I had the newest network drivers. It's working great with the Realtek RTL8125B NIC on my MSI motherboard. I'm getting up to 200MB/s copying video files between the machines. Doing a folder full of 3d files averaged between 120 and 140. It's now just limited by the size of the machine. I might now move the last 2 rotational drives from my workstation to the Unraid box, leaving just the SSDs in there.