Do you think my baby is ready for the next step in car seats?

[k.lee]

My six month old has started to try to try sitting up while she's in her car seat, swing, ect. I've noticed over the last two weeks, while riding in the car. she is lifting up her head and looking ll around in the car. She will not sit back most of the time. The straps are pulled as tightly as possible without her being uncomfortable. Should I go ahead and switch to the convertible seat? The seat she's using now is the Graco Elyse from Babies r us.