im my burban, im runnin pioneer head unit, two 6 1/2 pioneer 3-ways in the front doors, two 6x9 pioneer 4-ways behind the middle seat in the factoyr spaces (with a lil mod from a dremel tool of course), and two 12" kicker subs behind the third seat in a box that measures about 4' long, 2' wide, 2' tall divided in the middle so its like each sub has ita own area. note that right now i am in iraq and am giving a rough geusstimation of measurements but i know these are close. the box was a sealed box, which is good for the boom boom rap music, but i dont listen to that, i listen to country, rock and heavy metal and a ported box sounds alot better for that music. my question is what should the pvc piping i am using for my port measure. im not good with the math when it comes to this and could use an answer from someone good with numbers....thanks guys also i have a 350 watt amp runnin both subs, i know its rinky dink and i can go bigger with the amp , but whats my limit so i dont go too big and blow them out, subs and amp i was told by the shop that originally installed them that they were 2005 models....didnt know till then there was such a thing as year models with audio equip.