here's a link to the custom sound system install.
originally by celikazam The difference between a 15 and a 12 is that the 10 has less vibration but the bass is cleaner...12'z on the other hand will give you a cleaner bass and a harder vibration..15'z on the other hand, you gotta be psycho to put that in your car...if the 15'z are the JL W7
Ok, JL W7s dont come in 15s, for some reason the largest JL makes is a 13in., but dont let that fool you, these are still the best subs ever(what would you expect at close to $1000)
And as far as size of the subs, I'd go with 12's. they're tighter sounding than 10s, and 15 have always sounded kinda low quality to me. It seems like 15s are just meant to be loud(thus larger cone area so they push more air) and not clean. 3 12s would be great, and should sound great too, if you dont go cheap on the amp. You could have the greatest subs in the world and make them suck with a crappy 1200 watt Profile California series amp for 200 bucks(friend of mine)