I'm pretty big into child car seat safety (used to be a car seat tech at the fire station), so my decision on which car seats to buy was hard, but easy at the same time. I ordered them online at babyage.com. They had the cheapest Combi Shuttle price and you got free shipping with order of the Britax Boulevard. During Feb, Britax seats were on sale, so I decided to go ahead and buy that seat now, even though I won't be using it for a little while. Thanks to my mom, she bought the Combi Shuttle for me. :-)
I'm pretty happy with my choices. If you have any questions, I'd be glad to answer.
Here are some pictures of the seats installed in my car ('99 ford expedition). I'm such a car seat nerd that I played with them a bunch last night after they arrived.