I missed this thread.
R1: Amy Lee: 5
R2 : Rihanna: 4
R3 : Katy Perry: 4
R4 : Beyonce: 7 (Love her chest voice, hate her high register.)
R5 : Lady GaGa: 6
R6 : Britney Spears: 1
(Sorry.)
R7 : Avril Lavigne: 3
R8 : Madonna: 7 (I used to think that she has a nice tone.)
R9 : Keri Hilson: 4
R10 : Christina Aguilera: 10