Please help with a seat for a small 4 yr old

[Maru]

Hi all, your help would be greatly appreciated.
We have two girls 6.5 yr in a cybex solution and an original frontier. And DD2 4.5 yrs old 40" and 34 lbs she has boulevard the one that goes up to 65 lbs. and are currently shopping for a carseat for her to keep in DH car, which we are also shopping for. He is thinking of either a Nissan Altima, MAzda6 or Ford Fusion as we would need sometimes to fit a third person (adult) in there with the girls.
Any suggestions as to wich carseat would be best? If it could also be a seat that would fit her long (if it would be the last to buy better). And that it is not that bulky so thers is space for someone there.

Thank you

 

[ADEE]

I have my 4½yo (31lbs) in a marathon, we just purchased a radian 65sl for him.. hes tall but very lean. He looks great in both! I would prefer the radian in a smaller vehicle and you can find great prices on them if you shop it.. kohls has a great deal going on right now (20% off plus additional 15% off)