A P&P job isn't gonna net you that much on a stock B16 head. Maybe a 5hp in the upper RPMs. B16 head are already one of the best flowing heads Honda has, next to the "R" heads. The "R" head are nothing more than a factory ported B16 head anyways .....

If you're adding some bigger cams or perhaps some FI(Forced Induction) then the port job will amplify any of those mods. But as far as being able to tell a difference if that's all you're doing I wouldn't hold my breath.

Also, I wouldn't mill the head, if you're looking to up your compression, swap in some pistons to do that. Or at least a thinner head gasket. Milling your head is not revesable. That's just a personal peev on my part though.