No matter how you look at it.. there isnt a clear cut "best" Sundown driver. I do know however, that my SA8v1.5s do a damn good job playing all different types of music. If you dont cut corners on the install, I believe that any of their drivers will sound great.
Ive heard SA8 v1s, v2, E8s, and Nightshades (I think v2s).. and they all sounded awesome. Then again, Im sure they were in good boxes.