normally I wouldnt recommend using drywall screws either... but this is me being nit-picky
These are the only screws I would ever recommend anyone using to install an amp, subs, components or head unit.
flat bottom (so they dont chew on the mounting tabs) and tamper resistant.
The harder you make it for someone to steal your stuff, the less likely they are to mess with you to begin with.
My enclosures are not put together with these screws, but my subs are mounted with them, my amp rack is attached with them, my amp is mounted to my amp rack with them, my head unit (in my Dodge, since I havent finished the install in the Camaro) is installed with them, the dash kit is installed with them and I replaced the OEM trim screws with them so you cant even get the trim off without having the right bit... I HIGHLY recommend that EVERYONE use these type of screws for installing everything in their car/truck/etc...
and since I use different sizes and types throughout the car, lets hope that any thief that wants my stuff comes well prepared to sit and figure out which type and size to use to get it out.