I have been searching around all morning and have been unable to find out anything on this subject.

What is the difference between a 10" subwoofer / 12" subwoofer / etc. ?

I don't know if this will help me get a more specific answer but I'd be running 2 subwoofers, both dual voice coil, and both 500 RMS.

 

Not exactly sure what you're asking but both subs having the exact same specs, the 12" sub will be able to play a little louder due to extra surface area but will require a bigger box....generally the difference is (sume subs, same manufacturer, different size) is power handling of the 12 is higher, needs a bigger enclosure but gets a little louder.

 

so basically the bigger the sub the louder and deeper it can be?

 

Only if you compare between the same brand\model. You could have a 10 from one manufacturer go deeper and require a bigger box then another manufacturers or even the same manufacturer but from a different model line.

 

all other things being equal...the larger the sub, the more air it moves, hence, the more bass output you get and particularly at lower frequencies.

 

^^^ Agree.

 

Go Big or go home...

There is no replacement for displacement....

I'm not at all interested in being louder than anybody else or disturbing the neighbors, but i do surprize people who get into my car with how low the bass notes are.
I went with two 15's, strictly for the extwended lower frequency response

Yes, it will take more power to drive them properly.

 

I've listened to single 12" subs that will blur your vision and dual 15" set ups that sounds like a wet fart....

It's all in the power and quality combined with the box to give you the sounds you like...

Budet plays huge here...