I've been talking to S&W this week about a cage for mine. GREAT people to deal with. I'll be ordering mine in November (all cages go on sale!)
If you want to keep your back seat, you'll need to get their "prostreet" rear bars, they go through the speaker openings. Their regular race cage goes through the back seat area.
They can set you up with anything you need.
Their prices are right on with Summit/Jegs on the mild steel tubing type. Personally, I'm going with the Moly cage. More bucks but lighter and the tubing is smaller (but stronger)