Exhaust Size? Info.

[CateraMV6]

Hey guys I need some help figuring out the size of the 3.0L V6 Exhaust.  

What size is it... and is it stainless steel.  I am planning to do an X pipe at the front close to the brake points after the cats... and from there I plan on removing the two mufflers before the axle... and maybe replacing them with smaller resonators....

How much louder do you guys think it will get if I get rid of them... is it going to be unbearable... inside the car?

Any recommendations, anyone done this sort of thing..