My son (who is now 7) was in a similar situation. We went thru about 4 car seats, none of which I felt was as good as a
Britax. When
Britax came out with the
Regent last year, we got two, one for my daughter, who is 3 and one for my 7 yr old, as he can use it for at least another year.
He was in a
booster, a half
booster, etc. and an Eddie Bower 5 pt harness that converted into a shoulder harness. None of these seemed as secure as the
Britax. When we put him in the
Regent, he thanked us so much because he said he felt safer and it was much more comfy. It's still a 5 pt harness, which I feel better about.
Just my 2 cents. (Also, tinyride.com usually has the best prices and they ship for free)