I have a Magpul and love it...even for snap shooting
. It's rock solid and very comfortable. It also has the largest (I believe) butt plate, and you really do get a good purchase on your shoulder w/ it. It also has a longer length of pull in the last position (if that concerns you at all), even longer than an A2 I believe.
No, you cant' use the A2 buffer and spring. You must use a CAR buffer and CAR spring...get them Bravo Company-$11 for them both. Paul will treat you right, he's a great guy to deal with.
CAR Parts Go here to the bottom of the page.
I don't work for B/co, I just had great service from them, so figured I'd point people in that direction.
I don't know why the HotLink doesn't work...here's the URL:
http://www.bravocompanyusa.com/StandardCARStocks.html