It's easier to get specs from an online computer store for PCs and Macs that you can actually order right now, then compare published performance benchmarks for their processors and expand your selection if none of those are fast enough. You can't compare the whole universe of processors. I start with Dell's online store to make sure I'm looking at PCs that are currently available to order. Apple, HP, or wherever you're comfortable with, just to narrow it down to a small list of CPUs.
Then compare CPU Mark and Thread Mark numbers for your list of CPUs here:
https://www.cpubenchmark.net/CPU_mega_page.htmlFuture-proofing more than 3 - 4 years out is really expensive if not impossible. I like to pick a sampleset and say I have to be able to run at least that, with all the highest quality options, with headroom for a bigger load in the future.
I stress-tested my recent new PC using Nancy with 4 perspectives and all samples loaded, at full organ. The new i9-12900K handles that at HW 7 higher quality mode, 96k, 512 buffer, with some room to spare. It handles Caen Surround very easily.
That's about a 40,000 CPU Mark, 4000 Thread Mark processor. If you get an Intel or AMD around those numbers, you're good for a while on the heaviest current HW and sampleset demands. Yes, there probably will be fun new Hauptwerk options or samplesets in the next year or three that will make that inadequate, and I'll have to consider whether to turn off the new options or buy a faster PC.
There are server CPUs -- dual socket Xeon and AMD -- with twice that capacity, but the prices tend to be much higher than I'd be able to look at.
P.S. Clock speed and core count aren't good measures of CPU capacity by themselves. If you're comparing two nearly identical models, then those can tell you something, but otherwise not really. Performance on a known set of workloads is much more useful.