I've narrowed it down to the Britax Frontier 90 and Recaro Performance Sport.
Does anyone on here have experience with either model (hopefully in their X1)? Are you happy with yours, and does one fit the X1 better than the other? I'm looking for a "combination seat" (i.e. "high back boosters" with 5-pt harness mode that converts to a conventional booster later).
Here is the only picture I could find of either in an X1 (this is a Britax Pinnacle shown):
