What is your price range? There are tons of great seats in all price ranges. If you have the $$ I think you cannot go wrong with a britax seat. I have marathons for both of my kids and we love them.
Also, if you have not read about the importance of keeping your child rf past 1 year and 20 lbs, read here. Watch the crash test videos
http://www.cpsafety.com/articles/stayrearfacing.aspx
Here is a list of seats that we like on a car safety board I visit -
Convertible Seats
Fisher Price Safe Voyage Deluxe (FPSVD).17 inch top slots, 5-33lbs rf, ff up to 55lbs in a 5 point harness. Made by Britax, sold under the FP name- basically a stripped down Britax Marathon. Great seat, awesome price $129 (regular 199$), and will last most kids to age 5-6 y/o.
DISCONTINUED DUE TO POOR SALES
New Triumph Advance harness to 35 lbs rear facing and 50 lbs forward facing. Max harness height of 17". The new Triumph has the infinite harness adjuster too.. So no rethreading the harness! Much nicer than the old Triumph! Much taller shell than the old Triumph too! Priced at $130-150 VERY new seat so not in many stores yet I dont think.
Britax Marathon, Decathlon, or Boulevard. 17 in top slots, rf 5-33lbs, ff up to 65lbs in 5 point harness. Awesome seats, allow for rf tethering, has lock offs to replace locking clips, very easy installs, many bells and whistles that make them easier to use correctly every time, lasts most kids to age 5-6y/o. $220+ Check the FAQ sticky thread for a description of the three.
Sunshine Kids Radian. 18 in top slots, rf 5-33lbs, ff up to 65lbs in 5 point harness.Great seat, only second to Britax because it has some compatibility issues in some vehicles when installed with seatbelt. Really good seat otherwise, allows for rf tethering, lasts most kids to 6-7y/o. $175+
www.skjp.com has the manual available for viewing.
new seat from Recaro. Recaro makes seats for NASCAR and has made car seats for the European market and a few for the US market for years. it's a convertible seat that will rear face to 35lbs, forward face to 70lbs, and has 19" top slots. Bottom slots of 9" so not ideal for newborns...
The outside width of the seat at its widest point is approx. 19 ½ to 20.
The Como ($249) & the Signo are basically the same shell (vs. the Marathon & Boulevard where one has SIP and one does not) - the biggest difference is that the Signo has an infinitely adjustable harness (where the Como has to be re-threaded) and the Signo's latch straps are on a bar - similar to Britax (on all their models) - so you don't have to re-thread the latch belt if you're going from rear facing to forward facing.
And lower cost options... (for primary or secondary cars... they are still GREAT seats)
Cosco Scenera $40 (stay away from the one with the overhead shield!)
5pt harness version.. Very basic, no frills seat. Minimal padding, but it's rare for a LO to complain about it. 35lb rf limit with a taller shell! 40lb ff limit however most kids outgrow it in torso height at about 3-3.5yo due to the low 15in top slots.. It just doesnt offer enough torso grow room to get most kids to 40lbs. readily available at
Walmart/Target/Kmart. Usually requires 1-3 chunks of pool noodle to get a good recline.
-Safety First Uptown: 35rf/ 40ff/ tall 16.5in top slots so this is the ONLY rf/ff 40lb limit convertible that will likely get a kid to 40lbs. EPP foam, velvety plush cover, super cushy. Very easy to use seat. 8 yr lifespan! Around $100 at albeebaby.com, Target.com, and in store at Wal-Mart.
The Graco Comfortsport, Evenflo seats, and the Alpha Omega 3in 1 types are very small seats that are usually outgrown the same time as the $40 Scenera. You dont get much for you money. While they are safe there are just other options that offer more for the same cost.