As you probably know the i7 4790k has a 0.4GHz higher boost clock than the i7 4790. I found a i7 4790 for 130 euros and an i7 4790k for 210 euros. Now is the 0.4GHz difference worth the 80 more euros, or not?
I can't say that 0.4 Ghz is worth 80 euros to me. Get a good gpu that pairs well with the i7 4790 (like a gtx 1060) and you will be able to run pretty much anything.
The K version is 10-20% faster depending on the test. That 80 euros might be worth it if you are looking for longevity. It will be especially worth it if you decide to overclock since that is the main selling point of the K versions.
If i wanted to overclock I would have to spend at least 250 more euros for an overclockable mobo and a good cooler. Will the i7 4790 be enough for all sorts of games? Render time can be a bit longer, I don't mind that.
I can't say that 0.4 Ghz is worth 80 euros to me. Get a good gpu that pairs well with the i7 4790 (like a gtx 1060) and you will be able to run pretty much anything.