K.G.
I'm going to assume you need this for your 4 yr old. The only cons to the Regent is that it's a huge seat. It's also been recently discontinued in favor of the Frontier. The Regent has higher harness slots than the MA so you could keep your child harnessed longer. I have a 7yr old still harnessed in mine. I had a Marathon which recently expired and has since been destroyed and my 4 yr old was still able to fit into it. It would be a great seat for your new princess though.
The Frontier is a great seat with high harness slots and becomes a booster seat later on. It would probably be the last seat you'd need.
I'd highly recommend you go over to http://www.car-seat.org/ or the car seat boards on Babycenter and chat with a CPST (car seat tech).