Just to adjust the numbers a little, the Pi idles at 2-4W (for similar RAM spec), and the N100/150 are only about 2-4x more performant (with a slight bit less efficiency), for most tasks, in real-world benchmarks.
(Not saying they're not a good value, but you'd have to cherry pick a few benchmarks to say there's 4-10x performance.)
Dell/HP/Lenovo all have huge amounts of ex-corporate mini PCs constantly coming onto the second hand market as they reach the end of Windows 10 licensing, or are depreciated out, or mass upgraded. Some popular models to get due to having a full size PCIe slot are the Lenovo M920q, M720q, or P330. They idle at maybe 10-15W with no optimisation attempts, and you can put a 10G network card in for example, or a bunch of M2/nvme SSDs. RAM can be upgraded to at least 64Gb. CPUs can be swapped out, there are 3D printable rack mounts, backplates and so on in abundance.
I've had luck replacing Raspberry Pi's with Dell Wyse 5070's. They're not screamers, but they are relatively recent fanless hardware with low idle power draw and plenty of oomph to push every service I self host.
