Suggestions for a convertible car seat?

I need a car seat for a six month girl who is out growing her infant car seat. I need a seat that is safe and can fit rear facing in the back a PT Cruiser. I'm looking at the Alpha Omega Elite and the Evenflo Triumph Advance. Britax or Sunshine is not an option because of the price so please don't suggest it or make me feel guilty for not buying it. Does any one know of features I need to look for or have a suggestion for or against any seats out there? I'm totally confused. Thanks in advance for you help!