I'm rocking a couple of old cheese-grater Mac Pros. They're pretty mean machines: 12-core Xeons, plenty of RAM, but they're definitely getting on a bit (9 years and counting).

I don't feel any urgent need to upgrade, but I have nothing to compare them to. If putting together a new machine would cut my simming time in half, though, that could make economic sense…

So are there any “standard” benchmark scenes - and results - I can use to compare my machines to other setups?

(Blender has long had a standard scene people can render, and then submit their results to a Google spreadsheet: incredibly handy for comparing graphics cards. It makes it easy to judge whether spending a chunk of cash on a particular graphics card will be worth it)