RE: Barrel lengths
I don't have a KDF right here to measure, but I think they add about 1.5 inches. The Vias is the one I recommend to customers (those that I can't talk out of the idea). They are louder than a rifle without a brake, but not as loud as a KDF. Stubblejumper is 100% right - one shot without ear protection will cause irreversable hearing loss. I would recommend trying one of the new rifle rests, like the Caldwell Lead Sled or Benchmaster, instead. They cost about the same as having a muzzle brake installed - can shoot off the bench with comfort - and you will never feel the recoil under actual hunting conditions anyway.
Or else get your gunsmith to make up a knurled thread protecter to put on for field use.