We have a Britax Marathon 70-G3 convertible and we love it! Our son is 15 months old and is still rearfacing. We didn't start using it until he was 9 months old but you can use it as early as 5lbs (possibly needing the infant insert for better positioning). The things I looked at when deciding on a seat were safety features, ease of use, and affordability. Britax has excellent safety features like the integrated steel bars (reduces flexing of the seat during a collision) and side impact protection. With the LATCH system it is amazingly easy to use. It is also lightweight enough for me to easily move between cars. And finally, Britax has seats over a wide price range. They are great car seats and many are made in the USA. I suggest you do some research and take your new car to Babies R Us or Buy Buy Baby and try the seats in your car. You can't go wrong with a Britax! I am a member of the BRITAX Safety Squad - opinions expressed here are my own.
