WEll an SX likes 1200 wats and a XXX likes 1600+watts, i went from a SX 12 to an xxx 15, the XXX is louder but because its a 15 and it also sounds better, but at the moment im fighting with my system trying to get it to sound the way its supposed too, but you wouldnt unhappy with either, but if i was low on money an SX would fit that spot really good, but if i wanted a really good sounding system an XXX would be there, but to figure out which one is louder wil prolly start a long thread about SX peaks higher and XXX has more displacment but both will be loud