We have a Cosco seat in our truck as a spare seat. Gator's main seat is a Britax Pavilion. I really like the Cosco seat. All carseats have to pass the same tests so a 50 dollar Cosco seat is going to pass the same tests as a 300 Britax. I used Cosco seats
Our extra seats are also the Costco Scerena. So cost efficient and my DD is very comfy in it whenever she needs to be in it. Our main seats are Graco MyRide 65's. For 35 dollars, you can't beat the Costco ones IMO.
We have Cosco seats in our nanny and both grandparent's cars-we got the Scenera from Wal- Mart and I think its an incredible value. Certainly not as cushy as her Boulevard in my car, but for the short trips she takes with any of them, its perfect.
Re: 2nd car seat recommendation...
We have the Evenflo Triumph 65 LX for my mom's car.
We also use it for traveling so we don't have to worry about damaging our main carseats.