If you're concerned about quality in general and quality of welds in particular I would think twice about MAC. Someone recently installed their $359 Pro-Chamber. The fit was terrible and it leaked like crazy. I'm not sure if the guy cut it in half after removing it but someone posted a picture of the inside of one of these things. It looked like it was made by a 14 year old stoner on his first day of welding class.
I've heard a lot of good things first hand from guys in town. Seems hard to believe.