Need carseat recommendations for tall, skinny 3.5 yo

[wimom_02_05]

My 3.5 yo DS needs new carseats - he is nearing the height limit on his RA (35lbs, 42in) and his baby brother will need to move out of his Snugride (and into the RA) soon also.

What are the latest recommendations for older toddlers?

I'm not entirely comfortable with the idea of putting him in a CarGo type seat yet but my husband doesn't like the idea of spending another $500 on Britax carseats. I also want to be sure that it is a comfortable seat because several times a year, we drive 14+ hours to visit family.

Keep in mind that whatever seat we pick needs to fit next to an RA in a 2000 Explorer and a 2005 F-150 SuperCrew (where I think anything would fit).

TIA
Marcia

[Joolsplus2]

The Cargo is fine...it has a nice harness and EPS foam and is "just as good" as a Roundabout when harnessed. Maybe one of those and a Marathon? The Recaro Young Sport is also an awesome new seat that makes a great harnessed seat AND a great booster (compared to the Cargo, whih is kind of so-so as a booster)...here's a review and pictures of it, since it's so new of a seat http://uccomama-ivil.tripod.com/id14.html
Julie CPS Tech and mom to 2 in seats
http://www.cpsafety.com/articles/RFAlbum/SarahMA.aspx