Britax car seats are awesome, however, for the short time babies are in an infant seat (about 6-12 mos. depending on infant's size), I don't think the Britax Companion is worth the money (about $200). Sure, get one if you want, you won't be disappointed, but I think a Graco Safe Seat gives you much for bang for your buck. It's currently the only infant carrier that harnesses up to 30 lbs. and 32". (Most only go up to 20 or 22 lbs.) It has a 5 pt. harness and is fairly easy to install and is user friendly. I've heard nothing but raves from both parents and CPS Techs.
Whatever you get, be sure it has a 5 pt. harness and front harness adjuster.
Once an infant outgrows the infant carrier, I have no problem investing in a quality convertible car seat, because they use it for a long time.
More car seat and child passenger safety information in the "Resources" section above.