Car Seat Help!!!

Ok blogger mommies..I need your help!!  Makayla is getting VERY close to outgrowing her infant car seat and we're going to be buying a new convertible seat so it will last for a longer time probably by next month. 

I want your input!!

What are the best convertible car seats out there, in your opinion?  I know Britax has a really good reputation..I want something good because this is a car seat I am hoping she will be in for a while.  I also don't want to break the bank (I know Britax also comes with a price tag)..$150 or under would be preferable..but if its a little over I'd look into it if it came recommended.  I love her infant car seat but my only complaint with it is that even though its installed using the LATCH system..its never seemed like its tight enough.  And that worries me.  So I'd like something thats going to be easy to install yet sturdy while in place (if that makes sense).  And from the looks of it..the convertible car seats aren't removeable from the base (that is..like an infant one where you can take them in the stores with you..etc.).  To me..thats a HUGE bummer.  Alot of times she'll fall asleep in her car seat and its great to just be able to take her and the seat in the house..or in the store..wherever we may be. 

But anyways..please leave me some input..I'd truely appreciate it!!!!!!!!!!!!!!!