Britax Advocate--anyone have one?

My baby girl is currently 16 lbs 8 oz and 27 inches at 9 months old, so she is still well within the height/weight requirements of her infant seat. However, she is starting to fight, cry, and struggle every time I put her in her infant seat (or lay her down in the infant tub or changing table for that matter). A few friends told me that switching to the convertible seat will help because they can sit up (which is what she wants to do). I'm researching car seats, and it seems like the big kahuna on the market right now is the Britax Advocate. Does anyone have one? If so, what do you think? I drive a Toyota Corolla--do you think it would be too big? Is it really heavy to move between cars (my husband is deployed right now so I would have to move it myself if I choose to drive the other car). The price tag is steep, but I'm not basing my decision off of that because I saved money when I was pregnant for a convertible seat some day. I just want the best possible seat. Also, are the side cushion thingys on the Advocate effected by side curtain air bags on your car? Our Scion xB has side curtain air bags