I wanna know if its possible to build a ported box for 2 memphis pr 12's that will fit in the back of a grand prix that can push my db's from 141.1 to somewhere around 150+. I tried this box designing program called WinISD beta and it said if I built one double sized at 55hz I'd hit anywhere from 152-154db ranging from 50-60hz, but still somehow I don't trust that program when I seen it say that. Something just seemed a little fishy. I'm pushing 700 watts through the subs. I've seen 144's hit with the subs, but im looking to see if its possible to hit 150+ with them. If anyone can help me that would be much appreciated. Thanks.