its not meant to be a shock either, i know theres a few years between this and the haswell i3, so architecture has changed, but regardless of the lower clock speed as well, the formula is still the same pretty much, 2 cores 4 threads which is why i wanted to know specifically what the issue was if a newer i3 never gave me bottleneck. i could get a cooler and overclock to 3.6 or near there if that was the issue, but i doubt it is.
https://www.cpubenchmark.net/compare/Intel-i3-540-vs-Intel-i3-4130-vs-Intel-i5-2400S/738vs2015vs794
An i3-4130 has around 60% better single threaded performance, partly through the 0.33Ghz clock speed advantage, and partly through 3 generations of IPC improvement (~11% from 1st-2nd gen, 3-6% 2nd-3rd gen, 5% 3rd-4th gen).
Overclocking will make up some of that shortfall, but not all.
A 4130 may well run it well enough - performance in general is similar to the required i5-2400S, but going forward games are making better use of threading, so 4 physical threads will be more advantageous than the 2 Physical / 2 Logical i3.