Resource or site with seat info?

I want to start saving to buy my niece a new carseat. She is currently 30-33lbs, I am not sure how tall (at least 32+" since she is taller than my little one) and 2.5 - she is riding FF'ing in a RA. I know that when she outgrows this seat my brother will not have the $$ (or the knowledge) to buy her another harnessed seat. On Christmas I will measure her height and torso to get an idea (but I am guessing I have months to make the purchase/look for a deal).

So any sites/resources that compare weight/harness heights of seats?

you can always pick the brains of all the techs and parents here if there's a specific seat you're interested in with no specs listed elsewhere or to get a second opinion on any measurements, of course.

The Apex is only 99$ when it's on sale...same as a really nice booster. I'd think she has at least a year left in her Roundabout, though. The graco and evenflo combo seats have ~17 top slots, like the marathon, almost.

Thanks for the links! Once I get her measurements I will likely be asking for some feedback - my mom is going to go in on the seat(s) with me, probably for her 3rd birthday (not until Sept) unless she needs them earlier.

Should I be concerned about the Apex being used properly? My brother has done pretty well with getting the RA installed properly after going to a carseat check event (yeah for CPSTs!!!! - they made him reinstall it multiple times until he did it right! my DH went to the same event and they were super impressed with his install of our Husky and MA and sent him on his way). I worry about the requirement for the Apex to have particular height headrests - my brother is sort of a flake and I could see him forgetting that tidbit and they do move her seat from car to car a lot. Although I guess if I got her an Apex I could get two and he and his GF could each have one installed. Thankfully DN's mom (brother's EX) has a MA in her car - although I have heard from brother that she doesn't get the straps tight enough and has put her in in thick winter clothes and then drove through snowy conditions for hours to trade custody. This poor peanut spends way too much time in the car - I want her to be as safe as possible.

If you are concerned about your brother using the seat correctly, but he already knows how to use a Roundabout, buy Marathons or Decathlons. These seats are most likely to be used correctly and therefore will be the safest choice. Didn't you mention previously possibly returning one or both of the Decathlons you purchased after your accident and paying a restocking fee? Why not avoid the fees and give her a Decathlon?