Joel, I think it's a wise move. I believe the most common setup is XP10 in front and XP8 in the rear. At least that's what I run and most 1.8 cars. I don't think it's really different for the 1.6. The only time you'd want to go to XP12 in the front would be for a high speed track such as Road America.
Don't forget to adhere to the bedding procedure.
Spec Miata #20