What is the current vehicle year, make, model? What are your current carseats? (brand name + seat name please, if you can, but fabric cover design name don't matter)
I have not installed carseats in any of the vehicles mentioned, but the easiest sedans I know of for 3 across are the Taurus, Intrepid & Malibu.... However, the vehicle you already have may be sufficient with the right carseat configuration
(much less costly to replace carseats than a whole car)