what would the equivlalent be to the 6970 in nvidia, 570, 580? Is there a problem with going intel with ati, or amd and nvidia? do they mix well?

I would imagine those cards are the equivalent, more or less. The 580 GTX seems to be faster than the 6970, but it also costs more.
The best places to check would of course be guru3d, anandtech, tom's hardware...I don't keep up with the Nvidia side of things much these days...good cards, but I've got an Ati for now, so I don't see the need to know what's going on in the 'green camp'.

As far as your second question is concerned, there is no problems that I'm aware of mixing your Intels, Amds, Nvidia's or Ati's.

This is all you need

The 570 is approx same level performance and price. 580 is superior and more costly.

This is true of FPS. Flight sims suffer from a slow CPU (it really is the bottleneck in what we are concern).

So for flight sims, always buy the fastest CPU you can afford. Presently its the i7-2600K, followed closely by the i5-2500K. Remember that the newer i5 & i7 are faster clock for clock than the previous generation. See here:

http://www.tomshardware.com/reviews/...m-ii,2926.html

So get the best CPU with a good overclocking motherboard, then if you only run 1 GPU, you can live a less than 600W PSU, if you plan on running SLI/Crossfire go with a 750+ PSU.

In you case the last thing to upgrade should be the video card (GPU). Oleg's game seem to favor Nvidea. Don't know why? I prefer AMD myself. Here look here and decide.

http://www.tomshardware.com/reviews/...-590,2912.html

i am a amd fan to, i need to upgrade soon before the game released here.

Not really and certainly not if they thread it well. You need ram to have the game in memory so the cpu can calculate, you need it for the gpu etc. Also the fastest CPU wont help you if your gpu is crap, in all honesty COD does not push hardware components atm. The fastest i5 will not perform as well as a low range i7 in the future, you may have high GHZ but when my cpu can get double the work done with threading then yours can, you hit a cap where as I havent, because I havent even OCed it yet.

Also I would stay away from anything that is watercooled for a noob, unless he will learn to OC and maintain the system its not worth the cost.

I upgraded from i7 920 to a i7 2600k overclocked to 4.5 (basically the same as i5 2500k for this game) and I noticed a significant increase in fps and stutter reduction. I think this is something that is safe to upgrade immediately.

Wouldn't be so concerned about RAM as long as you have at least 4GB DDR3 now. I'm definitely waiting before getting another GTX480 though...

Absolutely. Water isn't needed for sandy bridge overclocks unless you go mad with your clock. I'd install water on my GPU instead of CPU for this game anyway.

What resolution do you run at?