We're pregnant with #4 (yay!) and this is the biggest age gap we'll ever have - almost 4 years. Our first three kiddos all used the same infant seat, that we got with DS #1, who is almost 8. There were _not_ very many options back then, especially compared to now.
What brand do you suggest? Here's our facts:
* we have big babies - they have all been 8+ lbs at birth and over 20 lbs by 6 months. The longest I used an infant carrier/bucket seat was 5 months because they outgrew it height wise. We grow heavy kiddos!
* we will need to buy a convertible as well, as our big boys are in Nautilus' and our 3 year old is in a TrueFit and will be still when the baby is born/little. I really like the TrueFit a lot - fits well, adjusts well (love the no-rethread adjustment) so I'm leaning towards that, although I could be swayed.
We have a Honda Odyssey and this kiddo will be in the middle captain chair.
We've had Britax in the past (hated them) and our boys are equally as tall (95%ile) as they are heavy, so the length matters almost more than the weight for us.