Subwoofer sound

I am planning on putting 2 12 inch subwoofers along with my 10 inch sub in my 1990 Trans Am GTA. I was looking at boxes and installation types and I see that some people install them upsidedown and others inctall them rightside up. Can anyone tell me the difference in the installation and how much different if any the sound is.

My understanding is that if you mount them upside down, they hit harder but you lose the super low frequencys.

(next time try over in the Cars in General > Car Audio section)

I don't think you want to use 3 subs, read here:

http://www.automotiveforums.com/vbulletin/showthread.php?t=233418



and for the reverse question, read here:

http://www.automotiveforums.com/vbulletin/showthread.php?t=233004