I have to 2nd the Graco Nautilus!! It harnesses to 65 lbs (a harness is 10X safer than a seat belt alone on ANY child as long as the harness is made for a child of that weight) , then becomes a high back booster to 100lbs or a low back booster if you so choose. It also has a 7 yr life span (CAR SEATS DO EXPIRE!) with the back on or if you use the low back booster mode in a few years, you get 2 more years of life on it making it a total of 9 yrs it will be good for...you can't beat that anywhere! It also has almost 19" top harness slots which is almost the highest out there. If you have a tall child, or even one with a tall torso (sit the child against a wall, and measure from their butt to shoulder..that is torso height), that is HUGE since once the shoulders are above the top harness slots, the child is too big for it..even if they weigh under the seat's weight limits, they CAN outgrow it in height first. My son is 3 and was already at the top harness slots in the Alpha Mega mentioned, sooooooooooo glad I tried it out at BRU before I bought it.
I got my Nautilus at Walmart.com in July for $127 but they are a little higher now. They can also be found at Babies R Us, Target and Baby Depot inside of Burlington Coat factory. Just to add, Consumer Reports isn't always the best bet for information. They basically report on what consumers are buying. Just because a Britax costs $300 doesn't make it any safer than my $127 Graco, they ALL have to pass the EXACT same safety standards to be put on the market. Yes, Britax has more bells and whistles but unless your child is in the car 6+ hours a day, is all that really necessary? My son has been in his Nautilus since July 4 and LOVES it. He loves his head rest, his HUGE cup holder and the 2 cubbies he has for his sunglasses and toys...and he's so comfy he falls asleep in it everytime we are out in the after noon.
Also as an FYI, your best bet is a hospital or fire dept where there is a CERTIFIED CAR SEAT TECH on duty. Not all cops are certified and most have no clue on car seat information. How do I know this? My dh is a cop and NOT ONE officer on his dept is certified..but there is 1 on his fire dept. and 2 on our neighboring FD. THere is also a website you can go to, to type in your zip and they will tell you where to find a tech in your area. I'll look it up and update this.
HTH and good luck
***** Here is the website to find a certified car seat tech in your area.
http://www.nhtsa.dot.gov/People/Injury/Childps/CPSFitting...