the most important thing is not speed/cores but rather ipc aka instructions per clock. this is how much work a single cpu core can do every clock cycle. the speed is how many clock cycles per second it can do. and the number of cores is how many cores can do those cycles. 1 ghz is 1 billion cycles per second!!
a low ipc is hard to overcome even with high speeds. for instance the old AMD fx series could hit 5 ghz but had such crappy ipc, they could not keep up with anything intel had at the time. software has to be written for more than one core and a lot of common stuff we use only runs on one core. so 2, 4 or 12 cores means nothing to that piece of software as it only uses 1 core. most games seem to need 4 cores minimum right now. some can use more if present, or are limited. every piece of software is different.
i actually have a q6600 system that was used as a gaming rig for a long time by the kids. with 8gb ram and an r9-270 it was good enough for most of what they wanted to do. i'd take the quad core over the other options everytime if in your position.
again speed is not everything, only one piece of the performance puzzle. in general the newer the cpu, the better the ipc. the only time speed can be directly used as a measuring stick is if you have 2 cpu's of the same generation. for instance an 15-4690k at 4ghz vs one at 4.5 ghz. since the ipc is the same, the speed difference makes the performance better at higher speeds. but 4 ghz on a 4690k is not comparable to 4 ghz on an 15-6700k and so on. the same goes between intel and amd as well. just because the intel chip can hit 5 ghz does not mean it is better than an amd chip that "only" hits 4.6 ghz.
right now the 5000 series amd chips at stock speeds out perform the intel ones at 5ghz+ due to the better ipc of the ryzen chips.