For what it's worth here is what I found when researching booster seats.
Video on UTube - talking about the dangers of booster seats.
http://www.youtube.com/watch?v=azgBhZfcqaQ
A good video showing why you should not turn your child to face
forward. The difference of impact on the dummies facing forward vs
facing back is incredible.
http://www.youtube.com/watch?v=Y2DVfqFhseo&mode=relat...=
Good website to mark to check on car seat safety info.
http://www.car-safety.org/basics.html
Britax Regent $269
http://www.tinyride.com/Britax-Regent-P977.aspx
Tinyride.com keeps them in stock and it's free shipping.
We broke down and purchased the Regent and LOVE IT. It's huge and we feel better knowing our son will be in a 5 point harness until he is 8 years old.
Good luck!
I did recently see a much cheaper seat that is a 5 point harness booster, but can't remember the name. It wasn't the Sunshine Radian, I think maybe it was Alpha????