Hey Rob, congratulations on the wedding, and the babies!!!


back in time we used Britax for the babyseats for older kids, as supposedly Britax seats are tested to higher speed limits than the other ones... Check this info, as this could be an urban legend...

We did not have twins, but I would suggest parallel carriage, so the kids do not get upset that you favor one over the other one... if one were older (not by minutes, but months/years) than the other, in that case the staggered setup is ok... for twins, gotta be equal... lol...
you might want to check into the ones that offer the carry-on seat that snaps onto the carriage, they call it "transportation system" or something like that... kids are simply growing from one module to the next. you have the base "permanently" set up in the rear, and the carry on moves from base to carriage.

Your X should have LATCH system, was standard from 2002 model on... allows anchoring the seats to the rear seat in no time...