hm ok thats the point I have AA on .. full ..
I've tried or tweak a little bit with the system.ovf (i'm not quiet sure about the name now) have you tried that or are you using the normal ingame settings?
I have a 6970 and I can only use AA if I play on single monitor at 1920 x 1080 for most good games. The games I have tried include Bad Company 2, Just Cause 2, Crysis, Metro 2033, STALKER: Call of Pripyat. Although I don't have AION, I believe that these games I have listed are similar to AION in the amount of graphical detail and strain on a PC that they would cause. If I use no AA I get 40 - 50s FPS in these games. If I use AA when using 5940 x 1080 resolution I get fps below 30 which I consider unplayable.
I have 8 gigs DDR3 at 1600, phenom II x6 1090T 3.2ghz, Sapphire 6970.
Originally I had a 5850 which I returned for a 5870 which I then returned for a 6970. During this process, I had the 5850 and the 5870 at the same time and tried using those in CF (It would be the equivalent of having 2 5850s). Even when using Crossfire 5850s, my frames were just hitting the upper 50s range for Just Cause 2, Crysis, and Metro2033 WITHOUT AA. I could use AA in BC2, Stalker and have 50s FPS tho. The 5870 is more powerful than the 5850 so if you got another 5870 you might be alright however you would still only have 1 gig of VRAM. You might consider this: http://www.newegg.com/Product/Product.aspx?Item=N82E16814102888&Tpk=sapphire%205870
It is a 2gig 5870 for 279 which is 100 cheaper than the 6970 so you could buy 2 of these for xfire and sell your current 1 gig 5870. Or get 2 6950s or 6970s lol.
Bottom line is that you won't be able to play Aion with AA at that high resolution with 1 card (maybe a 580? lol)