I had a close look at one of the 2006 trucks yesterday, there are the 3 front end styles... The chrome front end that goes from one side all the way to the other, and is metal... The plastic front end, where everything is painted the same color as the body... And then there is the half and half (Limited) front end, where the part of the bumper surrounding the fog lamps is plastic, and then there is a chrome piece in the middle... If I am not mistaken, the chrome piece in the middle should just pop off, and underneath would be the sport front end painted to match... Can anyone confirm this?

 

When you pop off the chrome piece you will not get a finished piece. you will have to get a new paintable piece to finish the look. I have a Laramie with the front chrome piece between the fogs. It does pop off though and does not look hard to replace.
I believe the 2500 comes with the chrome from side to side.

 

There are actually 4 front ends available on the '06s. The three official options you mentioned and 1 more. 27 of us are riding around in Laramie equipped RAMs built in September that were accidentally shipped with chrome Laramie grills and painted Sport bumpers (yep, even Dodge makes a mistake now and then!) It takes a lot of height out of the appearance of the front end of the truck. I have grown to love mine!