CDs for me. If you buy a big disc binder they really don’t take up that much room. Its about the same size as the 1971 compact OED that sits on the same shelf.

If I really wanted to get rid of them I’d just donate them to the local library system. The ones they don’t want they’d resell as a fundraiser.

I expect they will not be worth it as they’re too underpowered for your specific use case. (I’m assuming your use case is hosting complex physical similations for a major university physics department and the old computer you’re considering on Amazon is a used version of this one or something similar.)

For my home server I use whatever old PC I have laying around already.