If you go the amd route, I will warn you, especially since I hear electricity is more expensive in Europe than the USA. That 290 x you will need a hefty power supply, and I don't just mean watts. You will also need a water cooler. With your budget I can't see any reason to get. 290x. They are inferior to nvidia, the only reason to get one is for poor people like me lol. Even though I regret it now, because it ended up costing the same almost as a 780 ti.
I bought the 290x used, for 300, and a new water cooler for 160, with back plate. Any ways when I first turned it on to make sure it worked, and tested it, with stock fan settings it was going over 40c on a idle and 90 when taxed, which I found is normal for these cards. I tried to over clock it and it shut my PC off. So I had to upgrade the power supply to a single rail 60 amp, vs my 650 watt 16 amp 3 rail.
When I got the new psu which cost 100, now up to 560, which I could of got a 780, this card according to gpu z when over clocked draws 30 amps.
Anyways with the 3000 you have, converted to USA money. God USA money sucks compared to yours lol. Anyways, I'd recommended getting a 4770k i7 or i5, the i5 if all your doing is gaming. 2 780tis, custom water cooling loop, with atleast a 2 120mm fan radiator. 8gbs of ram, unless you are going to try running like 3 plus games at once, or something like that. A 1 tb 7200rpm for back up, and a ssd. That will cost atleast from new egg here around 3000. That will never not be able to play a game for the foreseeable future of gaming. Now at 4k triple monitors you would prolly get like 5 fps, but those monitors are really expensive so...
Although, i would also recommend thinking about cutting the costs of the CPU, and gpu. Change those 780s to 290xs, and get your self a nice 4k tv. Or if your more into the 3 screen set up 3 good 1080p monitors.
Now my personal recommendation since Europe has real internet, unlike my 2mb down, and 440kbs up. Cut out one of those 780ti, and get a 10 inch windows 8, android, or I pad, with at least 1080. Then you can play elite dangerous on the go if you have that legendary internet I keep hearing about. I use a dual band 600mbps wireless, cause that's all the new I pad can do, which I didn't know at the time. A anyways it streams 1080 p to my I pad, and there is no lag. Now I can only go around my house with it, but it's a must for me, because I usually don't get to just sit on my couch for long periods. So it's nice to be able to get up, and go where I need to, got 3 kids. It works well, it's easier or the same as a keyboard and mouse.
I'll end with if you really only want to play this game, you won't need a massive rig like any of that. I'll load up fraps, and tell you my fps in the alpha build, streaming to my I pad. I have a 290x i5 3570k oced to 4.5 8gbs of ram and no ssd.
I get in the first waste disposal mission 90-200 fps, that's not over clocked. Other ten the CPU, in windows mode max settings, streaming to the I pad.