Corn323

An AIO water cooler isn't going to noticeably change your temperatures from a high end air cooler like the Dark Rock 3.  Also, your CPU is less than a year old so there should be no reason whatsoever to upgrade, especially not at that price.  If you were going to upgrade you'd be far better off going with an Intel i7-7700k than either of the CPUs you listed, which at least in USD is like $329 and has decent overclocking potential with proper cooling.

Do not upgrade your CPU, wait until you wont be able to play in games that you play at 60fps on high settings. Only then consider upgrading. Oh, and overclock you CPU if you haven't already.
 
Case Closed, thank you

1700 @4GHz user here, I agree

1. Ryzen R7 1800X is faster than an i7-5930K
2. Don't get any of those, get an R7 1700 and OC it to get basically identical performance to a 1800X and call it a day.

Corn323 just dont make her pc better then yours =)

It's 3440x1440. 1440p is 2560x1440. An RX 480 doesn't really max out AAA games in 1440p. So don't expect to run games at ultra settings. 

i think you should wait till christmas or the holiday season when zen, kabylake, and possibly cannonlake are released. Save up your money till then and then you could get a really nice gaming computer

I'd replace it in pieces. The monitor should go quickly, in my surprising opinion, because it really is the weakest link here. The Q6600 is still a decent gaming CPU, and the 270X is a solid FPS card.
 
Is the PSU original to your PC? Because what you're describing sounds like a power supply that's getting ready to breathe its last. Honestly, if you're thinking 4K, you're going to have to spend a lot more than 600 Euros and replace pretty much everything, so take some of your budget and buy a really nice power supply now that'll take good care of your equipment and give you lots of overhead for overclocking. Here's the order I'd upgrade in:
 
1. Power supply
2. Monitor
3. GPU (for 4K you'll need at least a GTX 1070, ideally a GTX 1080)
4. CPU, motherboard, RAM
5. Whatever else is left in there that you don't want to reuse
 
Your GPU is still a solid 1080p option, although not for the newest AAA titles, and your CPU remains a surprisingly capable little gaming PC to this day. It's kind of like Intel's version of the Athlon X4 in that it refuses to go away.

waiting 3 months is well worth it

You can do much much better for the money. This system will play Battlefield 1 much better than the one you posted, and it's cheaper.
 
PCPartPicker part list / Price breakdown by merchant
CPU: Intel Core i5-6500 3.2GHz Quad-Core Processor  (€195.57 @ Mindfactory) 
Motherboard: Gigabyte GA-H110M-S2H Micro ATX LGA1151 Motherboard  (€62.96 @ Mindfactory) 
Memory: Kingston ValueRAM 16GB (2 x 8GB) DDR4-2133 Memory  (€64.03 @ Amazon Deutschland) 
Storage: Seagate Barracuda 2TB 3.5" 7200RPM Internal Hard Drive  (€72.76 @ Mindfactory) 
Video Card: EVGA GeForce GTX 1060 3GB SC GAMING Video Card  (€211.02 @ Mindfactory) 
Power Supply: be quiet! 500W 80+ Gold Certified ATX Power Supply 
Total: €606.34
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2016-09-23 02:44 CEST+0200
 
Tough call between the EVGA GTX 1060 3GB and the Sapphire Nitro RX 470 4GB at the same price though. 

With that mono you can't PC get a z170 type

Of course my post is assuming your power supply is still good. Maybe it's the culprit for your crashing and not the 270x? If you need a new psu you might consider something from Super Flower. I wish they sold directly in the US, they make really high quality units.

The intel build you have seems pretty good. What do you consider a "4K" build? The only real difference from a nice gaming tower and 4k build is the monitor.