Nice choice in truck, for sure. That'd be a sick ride. Fun thing about that is that you can find something that's like 5-10 years off a restoration, that can be driven while you freshen it up.
I'm a fan of Ford's myself, with a hankerin' for a late 60's-early 70's f100. Maybe even a 4x4 w/ a heavy duty pto winch up front for stump-pulling duties..(haha).
Certainly if you guys are simply outgrowing the XJ, it's definitely time to check out options.
For me @ 6'-0" tall, the XJ is a good fit. When my kids get bigger, I'll likely keep the XJ as a 3rd or 4th vehicle for my daugher's to drive when they're older. If I had to replace my truck with a bigger vehicle, honestly it wouldn't be within the Jeep brand.
I'd look hard at FJ80 landcruisers (7 seater), mitsubishi montero's (only the 7 seater version), and possibly even a series 1 or series 2 discovery 7 seater that has been well maintained. Isuzu troopers in the 2000ish range are known to be good trucks, too. They have lots of leg/cargo room, with the ability to run a rear-facing third seat, if need be.
Another option is the AWD astro-van. Lots of guys over on the expeditionportal have done a NP231 swap for true 4x4 ability, along with a mild lift and 31's. They then have a comfy 8 seater van that can take them a LONG ways down some pretty rough trails.
I've considered that idea, since astro's have a very reliable motor.
Just some thoughts for ya. Definitely can't go wrong with a FSJ, but there's lots of options aside from it, too.