Here is a list of seats with slot heights and weights:
Britax Regent - top harness height is 20 inches. Can hold children up to 80 pounds. Requires a top tether after 50 pounds.
Recaro Como/Signo - top harness height is around 19 inches (Signo is 18 inches, Como is 19 inches) and harnesses up to 70 pounds. This seat also rear faces so it can be used for babies up to school age.
Sunshine Kids Radian - top harness height of 18 inches. Can hold a child up to 65/80 pounds (depending on the model you buy). This seat also rear faces so it can be used for babies up to school age.
Cosco Apex 65 (also referenced as Safety First Apex, Safety First Biltmore and a few other names) - top harness height is at 17.5 inches and can harness up to 65 pounds. After the child outgrows the harness, the seat does convert to a booster. This seat does require a headrest behind the seat so it will not work in cars without headrests or tall seatbacks.
Britax Marathon, Boulevard, Decathlon - top harness height is 17 inches. Can hold children up to 65 pounds. This seat also rear faces so it can be used for babies up to school age.
Fisher Price Safe Voyage (based on the Britax Marathon shell)- top harness height is 17 inches. Can hold children up to 55 pounds. This seat also rear faces so it can be used for babies up to school age. This seat is being discontinued so it is hard to find.
Evenflo Triumph Advance (don't confuse with the original triumph which is actually a very short harnessed seat)- top harness height of 17.5 inches. Can hold a child up to 50 pounds. This seat also rear faces so it can be used for babies up to school age.
Safeguard Child Seat harnesses to 65 pounds. Top harness slot is 19" high.
SafeGuard Go Child Restraint harnesses to 60 pounds. It's harness is a little different and it depends on the seat back. Requires a top tether for installation of seat.
Evenflo Titan - top harness height of 15.5 inches. Can hold a child up to 50 pounds. This seat also rear faces so it can be used for babies up to toddler and maybe preschool age.
As you can see from the above list, the Titan isn't a good choice when looking at seats that will last a while. When they modified the seat, they changed the weight limit, but didn't alter the top slot height. At least with the evenflo triumph advance, they increased both the weigth and height.