Safest Stage 2/3 Car Seats

[icklescarab]

I've been trying to research the best stage 2/3 car seats for my LO and have ended up more confused than when I started.
I'm really interested in the top 5 for safety as we travel on the motorways a lot and I want to be sure I've done all I can to keep him safe in the car.
We have the added issue that he's fairly broad (potential rugby player maybe) so the seat needs to be a little forgiving for the chunkier toddler.
Please, please please can someone point me in the right direction?

Thanks in advance

Hi, i have aBritax Römer advansafix iv r car seat - cosmos black.
I got this from mothercare.
My daughter has just turned 6 and i have only just taken the 5 point harness off and she uses it with a seatbelt.
she is tall and the weight limit on the 5 point harness is higher than most of the others.
I have been very happy with this car seat and very easy to clean and take apart to clean.
Hope this helps. i was after a car seat that would keep her in a 5 point harness for a long as possible and was isofix. this did the job. at 5 and a half still in a 5 point harness i thought that was good. it will depend on weight of child. its untill 23kg. (i think) she has only just reached that.