Is this enough W for my build?

Yes. The Corsair CX600wV2 is a good quality PSU & will be sufficient for your rig.
The Antec HCG 620w M would be a much better choice, if you can afford it.  

CX is just ok, but it'll work.

A 400w psu would be more than enough for that system.

Are you sure? Like really-really sure that only 400W is enough? Because as I wrote only the CPU and graphics card can consume 600 Watts alone. Just check these links:

http://www.amazon.co.uk/gp/product/B004R7MTPQ/ref=ox_sc...
(scroll down)

http://www.amazon.co.uk/gp/product/B005UBNL0A/ref=ox_sc...
(scroll down)

If you still are then explain me detailed why, so I have a reason to believe you. thanks!

NB: I need to know it because Im gonna choose between these two PSUs:
http://www.dustinhome.dk/product/5010640894/corsair-gs-...
http://www.dustinhome.dk/product/5010596236/corsair-cx-...

The 6870 requires a 500 Watt or greater power supply with 24A on its +12V rail.
However...

from Ko888 ^

The CX600 with 40A on its +12V rail is quite sufficient for your rig. SO is the GS500.
Even the CX430 with 28A, would be sufficient. But considering your FX4100 to be OC'd, which is quite power hungry,
the CX600V2 would be a better/safer option.

Hi mortenfc,

As per your configuration, your PC can run fine on a 500w PSU whether you overclock it or not.

I would suggest you to get this one---
SeaSonic 520w Modular PSU---$70---
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

This PSU features Active Power Correction, has efficiency greater than 85%, delivers 40A on a single +12V rail and has two PCI-E connectors. It is modular too and I think it will be cheaper than Corsair 600w PSU.

This PSU will last for years delivering continuous and reliable power supply to your system.

Regards,
SmartGeek

Nah that one costs around 150$ in DK ^^.

But I still don't understand why really below 600W is enough because I filled a test for how much Continuesly Watt I'll need for my build and it said 588. Thats why I am looking at this: (And can you tell me how much Amp there are @+12, couldnt find it  
http://www.dustinhome.dk/product/5010462266/ocz-modxstr...

And can you tell me how much amp there are @+12V here as well, would really help me in choosing, cause I can't find any place on the net thats says it :S:
http://www.dustinhome.dk/product/5010640894/corsair-gs-...

Corsair GS500 +12V@39A.
OCZ ModXStream Pro 700W +12V@46A

Out of all those, I'd still say, get the CX600V2.

jonnyguru.com - Power Supply FAQ

Okay Tyvm, Ill get that one.