i did some measuring today and decided to throw caution to the wimd and have an available 7 cu ft befor displacement,i will still keep my back seat in my 2012 scion xb but i will have to figure out a way to easy acess the spare if needed,so i am now deciding between 2 15s or an 18 and i have a powerbass xta 5000 wich i would like to run at 2 ohm daily,so now i just need to figure out wich has more potential to be louder ,the 2 15s or the 18,the amp at 2 ohms puts out 2500 at 14.4 volts so if any recomendations can be given this old man would appreciate it,