WHAT !!!! Of the hundreds of boxes I've built, the only time I use screws is to hold an access panel OR if its a REALLY BIG box with multiple drivers. Of all the boxes I've built I have never had one blow apart at the seams - period ! I use generic Elmers on the seams, then follow up with a good QUALITY silicone caulk. All joints are air nailed with 2" nails every 3-4 ". The enclosure I have in my theatre housing an 18" is powered by a Peavey PV 1.3K (1300 REAL watts !! - Not the over rated power of todays car-fi amps) my Peavey blows 20 amp breakers just powering on !
IF you insist on using screws (IE: like to split every hole) AT least pre-drill and counter sink the screws with the proper bit ! The length of screw will be determined by the thickness you are screwing through and the type of material you use. For MDF, plywood and particle board use coarse thread. rule of thumb is softwoods use coarse, hardwoods use fine. ALLWAYS pre-drill !!
do it once and do it right.