it will depend on how often the other car gets used, and how often you migth get left with no carseat in your car

my bro started out with only one carseat, and after his wife had to call me more than once for a ride as he'd taken the car with car seat, they ended up having them in both cars....

it's a personal choice really, and one you have to work out yourself - would your DH take the car with the carseat often and leave you at home? if you go out as a family do you use the same car you use on your own during the week...? if you have a primary car and a secondary one, maybe get your Meridian for that one, and something like the Fisher Price one that was on spesh at target recently for the second car (half price, 149.50 - you might still be able to get it tomorrow , no deposit layby...)

my mum is getting the cheap one for her car so that she can take me places without playing musical car seats or expecting me to drive us all the time...