I run a 4790k, and I ran the numbers of what CPU I would have to upgrade to, in order to see any significant performance increase.
I came to the conclusion that in order to even make it close to being worth my while, I would have to drop money on something like a Threadripper, or the fastest Ryzen 7, not because there aren't Ryzen 7s or even 5s that beat my cpu, but because the performance gained would be so insignificant, the money spent might as well have been wasted (It's like spending 60 grand on a car that has 40 more horsepower than your car that has 260, and cost 50 grand)
The one thing that has pissed me right the hell off, though, is meltdown. People have been talking about different workloads and how they will all be affected, but what I found is, since the cache is flushed whenever ANY system call is made, it slows down EVERYTHING, to the point where I might as well not have any cache. I've noticed heavy hits with VMs and Disk I/O, but even things like video rendering, and just generic everydaying has taken some measurable hit because whenever a kernel call is made, it flushes the cache.
This is right quick turning me into a never Intel person. The flaw is incredibly stupid, and the fix is a joke. Even overclocking, which my 4790k is a darling for, hasn't helped close the gap enough. I feel like I have been downgraded to a slower CPU and am pissed off at Intel. The reason I went with them is because they had the performance option, and AMD was making 240 watt space heaters that required water cooling and a board with power delivery akin to a mains substation. Now that AMD is back in the game, my next CPU, whenever I get one, will be AMD. It's maddening that Intel, a company who has enough money to attempt multiple moonshots in the exact same historical manner as the Apollo program, decided to cheap out on security research and leave this shit in.
Anyways, after this rant, I have to say this. Intel has CPUs that perform well to this day, despite meltdown. Upgrade your weakest hardware, and keep your strongest.
I do actually have to agree with blueskull a bit here. Not on what to buy, but on the fact that workstation gear is reliable, but it's also expensive, and restrictive.