More CPU power don't speed up burning process. Burn speed depends from burner hardware and from media used.
To speed up burning speed use 16x quality media with your benq1620. Your burning times are in the mean (good times truly: my liteon 1633 require over 7 min to burn @ 12x :a )
64 bits plataforms will be really speeder only when 64 bit software will be developed.