It all depends on how serious you are about drilling straight into the vertical wall. I remember reading somewhere about someone that dropped the gas tank on his show car 2" to create enough clearance to mount amps and speakers, but the car wasn't something you would want to drive and park in the street; unless you have one of those car alarms like the Batmobile had in Batman I and II.
Anyway, your best bet is to create a rack for the hatch area behind the seats where the T-Tops are supposed to go. The roller shade will help a lot, but a smart thief that sees aftermarket speakers in the kick panel area will be smart enough to realize there's an amp or two driving them.