I used to keep up with car seats pretty well, but with my last baby turning 3 in May I haven't for a long time. The boulevard he is in expires in March so I need to get him something new. He is tiny, so he will be rear facing for a long time still, it's not even an option right now, since he's still under 20lbs and even if he was I'd keep him rear facing till past 3. I don't really have any $$ limit for it, most likely he will be in this seat till it expires, like I said, he is really small, and even my 9 year old isn't 50lbs yet and can still fit in a boulevard so we will get a lot of use out of it.
What seat to buy...
You are shopping for a <20# 3yo and you need a convertible seat? I'd look at the Evenflo Triumph65, Diono Radians, and Graco MyRide. The Safety 1st Complete Air is a nice seat, but has a RFing limit of 40": some people choose to disregard this, which is not something I'm comfortable choosing to do when there are seats that can be used with full compliance.
He will probably be 6 before he is 40", so that won't be too big of a deal. He has a genetic growth disorder and won't start growth hormones till between 4-6 years old (it's determined by bone age) so he's going to be extremely small till that point (and will never be average height).
I'll definitely look at those seats, thanks!