babytomato,
I would suggest to use infant carseat before 1 years old and change to convertible carseat after 1. My son used Graco Snuggle infant carseat when he's a baby (now it becomes my daughter's) and it costed around $70. After he's old enough for facing front, we got Britax Advantage (= Roundabout) from our friend. Now, we have 3 Britax carseats (2 in our 2 cars and 1 in the gargage saved for my daughter) and we like them. Although Britax is expensive, its quality worths. You can consider Britax Marathon which costs almost $300 and Roundabout costs around $270. I bought mine in Lullaby Lane when it has its semi-annual sale and I spent $240.
花旗太太生活在花旗國,留意時差,你問我未必即時答到。