Craig, that is definitely the easiest way to go. I was told to try a jigsaw, a rotozip, and a few other ways. I had to cut 4 holes for the mid range speakers and 2 for 10" subs. The Sub holes I tried using the jigsaw and the rotozip. both sucked bad. For the smaller holes, I figured I would try a 5" hole saw. It was perfect and very easy. Only took like 5 minutes per hole. Just make sure to use a regular corded drill. I started with a Dewalt 24 volt cordless and killed it halfway through one hole. A regular drill cut through like butter. Much more torque. Good Luck, and be sure to wear a mask and long sleeves. I was pickin the fiberglass outta my skin for days.
Rich