Check the Temps on your GPUs. I just recently had to RMA my XFX 4870 x2 because one of the GPUs was drastically overheating, and causing me serious performance issues (and threatening the long term usage of the part). I was running with PheII 710 x3 @ 3.35ghz with my old card (4870 512mb at 790/1050 clocks) managed to squeek out 15294 on 3DMark06.
I haven't (and don't plan on) OCing the 4870x2, as it is such a champ as is @1920x1080, but with my CPU now at 3.1ghz (highest stable clock at stock volt) and the 4870x2 my highest score is around 17k. So taking your x2 550 into consideration, You might not be that far off. My GPU scores scaled very strongly as I benched each step climbing through higher CPU clocks, not just the CPU score.
You would likely see a strong improvement in your 3DmarkO6 overall score if you overclocked the 550. You would see an even greater improvement if you had a stable unlock of your other two cores (your Mobo does support it.)
in Crysis warhead at 1600x1200 Full detail , 16 AA , Vsync , the fps are between 15- 30.
in COD 4 World at War at 1600x1200 Full detail no AA , 90 fp and can drops to 39.
Not sure with the 3d mark sorce off hand (to tired to think) but what bopped into mind just quickly reading over all of this is possible bottlenecking with the cpu? you can overclock that and see if it helps.
actually in some performance ranges ATI cards spank the nvidia in Crysis. The 4850 x2 for one beats all it's same price range Nvidia counter parts. That make it amazing test bed. Also to many of the big name games are optimized for Nvidia so you don't have much of a choice.
And don't forget that the drivers SUCKED when they first game out, hell there wasn't even drivers when it first game out. Over time all the 4XXX have had the bugs worked out and play the game smoother.