ported box size

I made a ported box with 3.1 cubic ft volume because some friends who maybe don't know exactly what they're talking about said that the bigger the box, the bigger the sound.  anyway, they also said you can use a rectangular port in place of a circular port of the same area without any problems.  so i did that too.  and also i didn't want to make it smaller than 1 inch wide, so that meant i had to make it long enough that it hit the back wall , turned the corner, and came about halfway to the front again.  i've always thought that the larger area of the port, the longer it has to be to be tuned to the same pitch, but a car audio guy at bestbuy just told me it's the other way around, that the two are inversely related, so what is right?  anyway about the box, it has a 1200w audiobahn 12" ultra excursion in it, and it sounds not like it should, i'm pretty sure, and there is almost no air moving in and out of the port.  should i chop the ends off the box and make it smaller?  is it better to have a round port than a slot?  what is the optimal diameter of a port?

thanks a lot for any help.

if you change the port you should be fine. make the port whole larger and shorter. either round or square all depends on your preferences. i believe square are usually used more for SPL setups.