I just purchased and installed an Alta exhaust for my 2006 MCS. Here is the full write-up that I did along with some pictures:
http://home.comcast.net/~rwkeating/auto/altaexhaust.html

If you want the short version of this article, here it is ... before settling on an exhaust, try to hear it in person. Plan on how you will get the old exhaust off. The 2 nuts by the cat. are the hardest to remove. It might be best to have a shop take those off for you. Make sure you have all the parts before starting. Make sure you have all the correct tools. The bolts/nuts from Alta are not metric. You will need a 7/16 deep socket for the V-bands. They give you one Alan wrench, but you will also need an 1/8" one. Follow the instructions. Take time doing the alignment as there are a ton of adjustments available to you. If putting on the battery heat shield, it will need to be modified so do it a few days later after the exhaust has been heat cycled and has had a chance to settle (and maybe re-adjusted). In general I like the Alta exhaust but I have some concerns that will require more time before I can make a final decision.

 

I've posted part 2
http://home.comcast.net/~rwkeating/auto/altaexhaust2.html

I had to replace the resonator. I now have Alta's new smaller resonator. In this write up there are pictures of the 2 resonators and sound clips from both. I also show some modifications that I did to better help support the rear of the exhaust.

 

Nice writeup on your install. Thanks for sharing!