I used to worry about this, but I've got enough furniture and accumulated stuff that the size of my car is irrelevant for moving house. My bed frame alone is too big. Hiring a transit van for a couple of days is about $50 and gives you over 2m of room inside.

Pretty much as soon as you buy a bed, your car is too small. And if you're at the level of self sufficiency where you own a bed, you probably own other things like chairs, tables and chests of drawers.