The safest car seat is one that fits your car, fits your baby, and that you will use correctly every time :). That said, I can possibly advise a couple seats, that you can look at and try in your car, and go from there.
The Britax Marathon (and Boulevard, I wouldn't much go for the Decathlon since you don't really need the infant insert if your daughter is already 20 pounds) is a great seat. They have very high harness slots, so that your baby can be harnessed for longer (which is VERY important! - I wouldn't go to a booster until I absolutely had to - each step "up" in car seats (rear-facing to forward-facing, harness to booster, booster to car seat belt alone) is a step back in safety.) The Britax seats rear-face until 33 pounds, and until the top of their head is within an inch of the top of the seat.
Another option is the new Evenflo Triumph Advance (NOT the Triumph 5/Premier/DLX/etc - VERY different seat!) It also has higher harness slots (about an inch shorter than the Britax), and can harness until 50 pounds. It rear-faces until 35 pounds. Again, you want to keep your baby rear-facing AS LONG AS POSSIBLE! The 1 year/2 pound rule is the absolute minimum - it's MUCH safer to rear-face to the limits of your seat (http://www.aap.org/family/carseatguide.htm). The only "negative" I have about the Triumph Advance is the knob feature to loosen/tighten the harness is not placed well (it's difficult to do rear-facing).
Less expensive options include the Cosco Scenera and the Safety 1st Uptown (both of these are great "2nd seats" or spare seats). They both have higher harness slots, but neither will likely get you to booster age (the max. weight on both is 40 pounds, but many kids "height out" of seat rather than outgrow by weight).
There's no way to know for sure if ANY seat will get you to booster-appropriate time, at least not a 6 months old - there's just no way to tell how your daughter will grow over the next few years. I've seen 7 year olds comfortably sitting in Marathons, and I've even seen 2 year olds that were too long-torsoed (total height is never an issue, since 2 kids can be the same height and fit into seats totally differently). I know that's not the answer you want to hear, but it's the honest truth. Don't we all wish we had a crystal ball to see though!
Also, I generally wouldn't go with what Consumer Reports says when it comes to car seats (other things though, they're usually pretty good). They don't release how they do their testing, and their "top picks" are not seats I generally recommend (The 'old' Evenflo Triumph, for example, as pretty low harness slots, and can be a bear to install; the Cosco Alpha Omega is HORRIBLE at pretty much everything except for kids under 30ish pounds)
No matter what seat you choose, please find a local CPS technician, who can look over your seat and make sure it's installed correctly. There are quite many in the Pittsburgh area; many are police officers, EMTs, firefighters, etc. It's a perfectly free service, and one that is very important (we want your child to be safe in the car as much as you do! To find a tech in your area (Pittsburgh is a big area, lol), go to www.seatcheck.org, or locally www.patechs.com
One more thing (sorry for the adding!): The Cosco Alpha Omega (Elite or otherwise, also called the 3-in-1 sometimes) is NOT (ever) the only seat you will ever need! All car seats expire after 6 years, and ALL CHILDREN need to be in boosters until they are at least 8 years old. Add to that the fact that the seat has very low harness slots, most kids grow out of the harness way before they can (or should) be in a booster. And it's not a very good booster (2 cents here)