It sounds like your looking into more like a convertible seat. They really are not ideal for the newborn phase. Also, the Smart Seat is a huge pain. If you are dead set on a convertible car seat then look into the Maxi Cosi Pria. It's the only real convertible seat that truly is rated for newborns. The rest say they go down to newborn size, but they don't really fit.
Personally, I would get an infant bucket seat and then go spend the money on a Diono Radian RXT when the kid outgrows the infant seat. This way you have the 2 seats you will need from birth until they are 120 lbs (RXT goes to a booster). For infant seats I like Graco Snugrides (the regular 22lb one) or a Maxi Cosi Mico (which is what we have until DS can fit into his RXT). Both will be perfect from the newborn to 6 month phase when they will transition into a convertible.