OK, is 4 gigs of 1600 is better than 6 gigs of 1333? This is what i've got now:

You can't use the 6GB kits on sandybridge systems as they are tri-channel rather than the dual channel required. If you can go for 8GB 1600MHz, then that would be the best bet imo. You can get 8GB 1600 kits for next to nothing in the UK so it's not a massive expense. Not sure where you are (Sweden?) so pricing is up to yourself.

Ok, so 2 packs of the RAM above (Corsair 4GB (2x2048MB) CL9 1600Mhz XMS3 1,5V) will do it? EDIT: Or rather the pack with 8 gigs directly, so i save some money :P

Get the 8GB kit. 2 sticks are going to be more stable than 4 when overclocking, so look for a kit with 2x4GB sticks.

OK, what about this: Corsair 8GB (2x4096MB) CL9 1600Mhz VENGEANCE BLUE And do i really need 700W PSU? Can i go with the Corsair CX 600W V2 80+ or the Corsair TX 650W V2 80+ Bronze instead?

Use the extra money you saved on the 560Ti. It's a little but more, but it's worth it. Check the link for the difference between the 560 and the 560Ti. http://www.videocardbenchmark.net/high_end_gpus.html

And do i really need 700W PSU? Can i go with the Corsair CX 600W V2 80+ instead?

You should only be using around 450-500W with the system you have built...I have almost the exact same specs. Go with the 650w PSU to be sure; you never know. But if you wanted to get a second GPU in the future, you would have to upgrade your PSU. This is the site I used to calculate your PSU usage. I tried to put everything in as best as possible and it came to 485W. If you decide to stick with the regular GTX 560, the usage will be lowed. http://extreme.outervision.com/PSUEngine

Okay, then i'll go with the 650! Whats best? 4 gigs of CL7 1600 RAM, or 8 gigs of CL9 1600?

Okay, then i'll go with the 650! Whats best? 4 gigs of CL7 1600 RAM, or 8 gigs of CL9 1600?

As clum said earlier, you will have a difficult time telling the difference between CL7 and CL9 RAM. FSX will never use more then 4 gigs of RAM. If you want to run programs in the background, then 8 gigs it is. It's your call.

Okay, thanks!

Looking decent. One thing I would change is the PSU. It´s with 600W a bit low. Maybe you can get an 750W instead.

Trust me, my friend has an i7 2600 system with GTX 460 and blu ray and 600W is plenty. If its good quality it will generally put out more than its rating.maybe 650W for future proof, a HX650 would be a great choice.