If you like the older version of the Triumph, you'll probably like the newer Triumph Advanced -- it's very easy to use, comfy, fits most vehicles properly & fits most kids until they're truly ready for a
booster 
It has a higher
RF weight limit than the
Marathon, but cannot be tethered
RF (tethering is a nice safety feature, but not required &
RF without tethering is still sooooo much safer than
FF)
What is the child's age, weight, height?
What is the vehicle year, make, model?