Cutting doors for speakers

[Longhorn Man]

Keep it stock, don't cut them....

I'm cutting my doors for speakers. I need advice on how to do this without screwing it all up. I want to mount the speakers inside the door, from behinde the sheet metal. However, I completely suck at cutting straight lines, let alone intentional curves. What would be my best bet? I thought about my air cut off wheel, but the curves would kill me when the wheel shatters. I have an air nibbler, but they don't seem to good for slow cutting and don't seem to be too good in turning. Is a jig saw the best route?
Also, how do I determine the hole size since I want to mount behind the panel?

I plan on getting the lower door carpet kit and putting it over the speaker. I'll poke holes in the back side of the carpet to let the sound travel through better. I know it won't be accusticly invisable, but it will reduce the muffeling effect.