Britax Marathon G4.1 Convertible Car Seat – Link 
Walmart has this – in the Beckham color only – on sale for only $119.88 w/ free 2-day shipping!
This has a top 4.7 star rating on Amazon and normally sells for about $230.
- Safe Cell Impact Protection is an integrated system of safety components, including an Impact Absorbing Base, Tether and Harness, an Impact Stabilizing Steel Frame, and Complete Side Impact Protection.
- Safe Cell Complete Side Impact Protection surrounds your child in a deep protective shell designed to absorb crash forces and shield your child from debris.
- Quick-Adjust, 10-Position Harness and 2-Position Buckle allows you to easily move the harness upward and buckle outward for a comfortable, secure fit as your child grows.
- Easy-On / Easy-Off LATCH Connectors lock into place with an audible click and are easily released with the push of a button.
- Tangle-Free, 5-Point Harness prevents the straps from twisting making it easier to load your child into the seat and ensuring a safer ride.