Based on previous VA's - I would prefer Knuckles to sound like either Dan Green or Travis Willingham, Scott Dreier's voice also sounds really cool too! I would prefer Knuckles to sound more aggressive, as the he is a central character to the plot and goes through some tough times. 

Believed to be the last of his kind, Knuckles is the stoic guardian of the Master Emerald. Despite being Sonic's rival, they've often worked together to recover the Master Emerald from the villains who sought to steal it. His spiky fists pack a mighty punch and enable him to climb vertical faces with ease.