we went from the infant carrier to britax roundabout.. but the roundabout only goes up to 40 pounds and 40 inches.. (which is about 4 years old..) so my tall children will grow out of them soon...
we love the britax.. it is a great seat comfortable and easy to install. the straps do not twist.. it is a great seat.
so we recently bought 1 graco nautilus... it goes up to 100 pounds and a lot of inches... (basically an 8 year old..)
The law in michigan is kids must be in a car seat until 8 or 80 pounds.. so you might want to get one seat taht will hold them until that age.
the graco nautilus is a good seat..but the crotch strap is too far back and hard to latch. that is annoying. the straps do twist a bit.
Whateve seat you buy.. you will probably need 2 car seats in this size.. one for moms car and one for dads car... so it is pretty expensive..
I bought my britax seats used on craigslist.. I will sell them when we are done with them - probably for what I paid for them.. you can usually find britax used .. it might take a few weeks to find one in your area.. but they are out there used for a lot less money.