T.
Britax car seats are the best!! We have not used anything else since our kids got out of the carrier. My kids are 4 and 6 years old now. Yes, we bought 2 of everything so both cars would be well equpped. I did not ever want to have second thoughts that if only he/she had been in the Britax they would not have gotten hurt. I know the Britax car seats are expensive but consider what your child's safety is worth!!
That said, here are a few things to consider:
1. Will your son be able to stay in the carrier safely until he is 1 year old AND 20 pounds? My kids got too heavy for me to lift in the carrier before they really outgrew it so I used a convertable seat (Britax Roundabout) which goes up to 40 pounds. If you need to move your child out of the carrier before he is 1 year you will need the convertable seat that can be rear facing now and forward facing later.
2. If you go with the convertable seat, consider the weight limit of the seat AND the weight limit for using the LATCH system in your car (check your owner's manual) We moved my son (now 6) to the Britax Husky (which is only forward facing) when my daughter was ready for his Roundabout. The Husky has a weight limit of 80 pounds BUT the weigh limit for using it with the LATCH is much lower for our Honda Odyssey. My son had exceeded the weight limit for the LATCH so we tried installing it with the seatbelt per the instructions. It did not seem secure at all! It moved from side to side way too much!! We decided to re-install it with the LATCH and use it for when my daughter has a friend riding with us. We bought 2 Britax Parkway boosters for my son so that he and a friend can ride safely without having to move carseats.
3. My 4 yr old daughter rides in the Britax Regent (the newer version of the Husky). Although she could still fit in the Roundabout weight wise, she seemed too tall for it a long time ago so we moved her to the Regent.
4. If your son seems to be big (weight or height wise) you might want to consider the Britax Marathon. I think its weight limit is 60 pounds (MY 6 yr old weighs 50 pounds and my 4 yr old weights 35 pounds, just to give you an idea). Just be sure to check the LATCH limits and try installing it in your car both with the LATCH and with the seatbelt before you buy. We did not try before we bought and might have bought different Britax models if we had.
Righ now, my hubby has a Britax Regent and a Britax Husky in his car. His car has higher weight limits on the LATCH so it is still ok for my son.
I have a Britax Regent, a Britax Husky, and 2 Parkway boosters in my van. I can carry 4 kids at all times which is nice.
Hope this helps!