Why are you having trouble understanding that the consensus here is THE PART THAT YOU ARE MISSING is that your entire premise for comparing the cards is FLAWED. Lets see at least 8 or 9 posters have told you to try playing some games to see if you see more improvements, yet you continue to ignore that and defend your choice to use 3dmark06 as a means for comparison.
This thread is going nowhere because you just don't want to listen to logic.
Maybe if you go and play some games and then come back and say that you see no difference people will let up criticizing your use of 3dmark06 as a comparison, but instead you are choosing to be obstinate.
This was your thread asking for advice and you don't like the advice you are given. So it is pointless for the rest of us to persist in repeating the advice and our reasons for giving the advice and thus I will no longer argue with you.
Edit: In attempt to leave the thread on a more amicable note, I link you to this review
Legit Reviews 4870CF and 4850CF results
3dMark06 results
4870CF 17956
4850CF 17708
similar to your results of a 227 point increase they found a 248 point increase or 1.4% increase
Gaming benchmarks
Bioshock 1280x1024
4870CF 92.2 FPS
4850CF 76.4 FPS
20% increase
Bioshock 1920x1200
4870CF 57.7 FPS
4850CF 47.2 FPS
21% increase
COD4 1280x1024
4870CF 179.9 FPS
4850CF 129.6 FPS
39% increase
COD4 1920x1200
4870CF 121.9 FPS (nearly as fast as 4850CF at 1280x1024)
4850CF 88.1 FPS
38% increase
of course there are some games in there that also don't scale well with crossfire anyway.