I had been going back-and-forth between the 3-gun M2 and the standard M2 (24"). I decided on the standard model (as I am a newb to 3-gun) and may in the future send it to TTI for the full spa treatment. For just a little more he lightens up the bolt carrier, refinishes it and modifies it for ghost-loading. There are also a couple more features that appeal more to me over the standard Benelli 3-gun. The mag extension is also included in the package where the 3-gun is shipped 3+1.
There's the first post/newbie intro.
....that being said, Euro Optic has a new 24" 3-gun M2 in stock for $2199. If you're a Sniper's Hide member they'll take off a little more.
Good luck!