RAM speed?
2666
2666?
Yeesh. Can't get above 2,133 without overclocking.
That processor you mentioned isn't particularly great, so I'd say this is strong evidence that RAM speed rules the DF roost.
In my fort, the undiscovered undead hordes in the caverns tank the FPS more than all the other factors combined. Reveal all from DFHack showed that rather than the 300 other units I thought I had, there were well over 1200...
The RAM timing is equally as important as the cycles per second. 2,133 MHz with 10-12-12-24 would be about as fast as some 3,200 MHz with 16-18-18-36 timing.
Every 12 clock cycles, the first passes data to the CPU, doing 2,133,000 cycles a second. That's 177,750 data transfers per second. Whereas the second performs 3,200,000 cycles a second, passing data only every 18th cycle. That would be 1,777,778 data transfers. Only 0.0016% faster. Put another way, these 2 hypothetical RAM sticks would have identical FPS all other factors being the same.
Dwarf Fortress deals with many small calculations rather than massive ones like you would find in video editing applications, so the GB specs of the RAM doesn't really give you any advantage. The cache size of the CPU may have more of a role to play there.
TLDR: You can save a lot of money and potentially even build a faster PC too if you do a some research into all the specs of each component. Timing was a new one for me. I thought it was all about clock speed before my last build.