Bump with new question

I hit 0.5 bar at 3500 RPM and full boost 1.5 bar at about 4500 with 2876 .86.
I found a Rear AR .64 For the 2876-
What will be the difference with 2876.64 campared the 2871.64?
It will be easier and cheaper to change only the AR instead looking for new turbo.
So your opinion is important before purchasing one of them:P
Thanks!