Swapping out factory muffler with Spintech

Hey guys, I'm about to swap out my factory exhaust for a Spintech muffler. I'm thinking of going with the same muffler I had on my new body style GMC Sierra SLT Crew Cab Z82 Texas Edition. I had the Spintech 6000 Pro-Street. I have an Armada, so I'm wondering if the Pro Street will be too loud for an SUV. It was perfect for my Sierra, although I was wanting to upgrade to a Super Pro Street as it's their loudest and much deeper than their second loudest Pro Street.

What does you guys think? Would it be too loud for an SUV? It will be dumped since from the muffler on back, the exhaust tubing fell off, so I'm not going to mess with it. Should I go with the 3rd loudest, especially since it will be dumped? I swapped out my Flowmaster 40 Series and absolutely LOVED it! I will never go with another exhaust, except maybe on a car, than Spintech. They are damn near bullet proof, have the best sound, deepest sound and very throaty.

Here is the most important question. What size do I need to get? I haven't decided if I am going to weld it up or use clamps, because I believe my Mig welder tank is out. So I need to know what size diameter goes into the muffler.

Any help with people who have ran Spintech mufflers, especially the Pro Street 6000, is much appreciated!