from what i remember from a friend that is a car seat safety tech, impala's are very wide. but, you do have two massive car seats, i know - i have had 7 britax car seats! personally, if i were you, i'd get a minivan, but you have said that's not what you want. if you find a sedan that will fit an adult in the middle, what you need to consider is HOW the adult is going to get in the middle, they'd basically have to climb OVER the carseat on the side, b/c i know the britax seats sit up quite a bit. another option that was mentioned was the sunshine kids radians - i have two radian 80s in my husbands car b/c that is really the only carseat that you can fit three across, and we just had our third child. the kids are rarely in his car, but you never know... they are NOT sold "only online", there's a few stores in this area that have them - the one that comes to mind is lonestar baby in frisco. in my opinion, they are not as safe as the britax, but they'll do. we use them for hubby's car and for travelling(they fold flat for easy backpacking through the airport). anyhow, good luck - hope you find a solution that works for you!