I have this seat (the no speaker version), we use it in both a corolla seca hatch and a commodore station wagon.

We did not need an extension strap, the requirement for this depends on where the anchor point is located in your car.

I love it, but for our next baby I will be hiring a capsule for when s/he is a very small baby, just because its easier to take the whole capsule in and out of the car, and a lot less disturbance for bub. However this is the same for most of the car seats I have seen, not a commont on the SNS AHR in particular.