Question Britax Roundabout vs Boulevard

I know I want to go with a Britax but I'm not sure which one of these I want to go with! My son is very little for his age, he's 9 months but wears size 2 diapers and can still fit in some 3 months clothes, weighs 21 lbs. Even though he is small he has reached the limit of one inch away from the top of his Graco infant seat. Since he's so small I'm sort of leaning toward the boulevard but I don't know!!
Also I drive a two door '03 Pontiac Sunfire this should fit prefectly right?
THANK YOU!

It's hard to compare the RA to the Boulevard because the BLVD has the True Side Impact Protection. Personally, I would do the Boulevard or even the Marathon, as they will last MUCH longer than the RA. The Roundabout is very nice and probably has the easiest harness adjuster of any seat. However, the price tag is pretty high for a 40lb limit seat. You can get Marathons for just about $20 more right now and that is a much better deal.
I have had an RA and currently own a Marathon. I definately feel the Marathon is worth the money. My RA was nice, but not worth the $200+ price tag(IMO).

To answer the 2nd question, you can install a RF seat more upright for an older child, meaning it will take up much less room front to back... you can have it closer to 30 degrees rather than 45 for an infant

For size... this is my 31 inch 21lb babe at 17 months old... same size as yours. Car is a 4dr Buick Regal... wide seat, but not so huge front to back DH still had plenty of leg room though!
http://i292.photobucket.com/albums/mm16/sunnywallace/Boudreaux/12-18 months/2008-02008.jpg

I have owned a Roundabout, Boulevard, and two Marathons.

The Roundabout has a much shorter shell height than the Marathon and Boulevard. Also, the roundabout has a 40 pound weight limit whereas the Marathon and Boulevard have 65 pound weight limits. The Marathon and Boulevard have very similar shell and harness heights.

While I did really love our Roundabout, my son would have outgrown it by height far sooner than the Marathon or Boulevard.

This is a picture of him in a roundabout at 16 months old. He was about 19 pounds in this picture. Note how much room there is above his head.



This is him at 3 1/2 years old in a Marathon. He was 27 pounds, 36 inches in this picture. Even with his growth, you can see he still has plenty of room above his head.



Since you have a 2 door vehicle, it will likely be more difficult to get your child in and out of the carseat when it is rearfacing if you get the boulevard, because of the headwings. If I were you, I would keep this in mind and try out the seats in your car at babiesrus before you purchase one of them.