B.W.
Graco MyRide65 is $150 and will rear face to 40lbs and forward face to 65. Its the same shell height as the Britax Marathon so it will last most kids to at least age 5/6 in the harness.
The Britax Roundabout50 at Target is $160 and will rear face to 40lbs, forward face to 50lbs. Same height as the Marathon.
Good for you for wanting to continue rear facing. Its the safest! THe MyRide is a great seat for the price you will be happy with it.