An anti-recommendation here:
I got a Britax renaissance for DS when he was 9m old, it was one of my best purchases and I raved madly about it, gave it a very good grade in a review, etc. And it was good and confortable for a 9m old, a 12m old, and 18m old and even a 2 year old, but since he was a bit older that that it is not one of my favourite ones at all:
It is sooo tall that it is a bit fiddly to seat DS on it, I have forgot the amounts of times I have hit DS's head against the roof. Now DS is a bit bigger it takes me ages to strap him down because it takes for ever for him to manage to get on it (the seat looks like a tower and DS is in the "I do it!" phase. The straps are not long enough to strap him if he is wearing his coat, so another bad point.
DS is only a 50 per centile, who is going to be 3 yrs next week. No way on Earth he could fit in it for another year, and... he is still too small for a booster seat (the ones without a back), so I guess I will need to spend, again, a good amount of money to get something to do the work in between...
So, my advice is to get anything that is lower and wider than a Britax Renaissance.