I'll add another vote for sticking with haswell. Either an i5 or i7 will be the best upgrade for the money. If it's a z series motherboard you have consider the k series cpu's and a decent aftermarket cooler to overclock it a bit. The slight performance increase with skylake isn't worth a new cpu, mobo and ddr4 ram along with reinstalling windows.
Continuing with that logic, if it doesn't make sense going with a whole new cpu, mobo and ddr4 ram for skylake it certainly doesn't make sense to go with a new ryzen cpu, motherboard and ddr4 ram along with a reinstall of windows simply because it's 'close to haswell performance'. Best case scenario is an unnecessary and expensive sidegrade.
Broadwell cpu's are few and far between, they offer no significant advantage and often perform worse than haswell refresh/devil's canyon. Their only real boon was the improved igpu which hardly anyone uses. Haswell's igpu is plenty for basic tasks, if someone is going to game they're going to use a dedicated gpu 99x out of 100.
I'm not sure what StupidComputers is talking about, they may not be familiar with intel motherboards the past 4-5yrs. Software overclocking is a poor way to go about it, overclocking through the bios is preferred. Software cannot overclock or unlock the cpu via some magic if the motherboard doesn't support it. The only way to achieve any sort of overclock on all but maybe 1 or 2 non z series boards is through baseclock (bclk) overclocking which nets very little performance before creating instability. Only k series cpu's have an unlocked multiplier and to take full advantage you should use a z series motherboard. Some bios' versions attempted to skirt the overclocking but microcode via bios updates and windows updates closes that.
Contrary to StupidComputers suggestion there's no reason to get a 4790k over a 4790 if you have a non z board, there is. The fact the 4790k is 400mhz faster out of the box, it's not the same as the i5 4690 vs 4690k where they share identical factory clocks out of the box. For the extra price you're getting a faster cpu with the 4790k whether you overclock it or not.