As part of our move to the suburbs, we are purchasing a second car for DH to commute in. I'd like to start off with just one extra convertible carseat in that car, in case we want to use it on the weekends to run out quickly with just one of our older DDs. So I am looking for a seat that I can adjust easily for my 2.5 year old / 4.5 year old (who are not all THAT different in size, but the 4.5 year old is obviously taller) - I don't want to have to remove the seat to adjust it - if I'm doing that, I might as well just take the seats from my SUV.

Any suggestions? The cheaper the better; I'm tempted to just get a Cosco Scenera, but I suspect something with a no-rethread harness might be better.