RBAC Extensions. Which is the best? Why?

Hi!

I need in my app good permisions system.

So in Yii i have to use RBAC.

I need 3-4 levels on front end, and 2 on backend.

Which extensions for RBAC is the best in your opinion for my app and why?

Please give me tips, because i cannot spend time for testing and searching good module…

RBAC is extensionly and fiexibly, so if you want make a best job, you should do it by yourself.

I used some RBAC extensions downloaded, but they possible need for me.