There are easy ways to avoid that. Even then, I doubt the difference would be very large.
I had a sub setup in my eg sedan, still sounded awesome.
Small sealed box with 2x12" subs.
Also had one 12" sub powered off 300wrms in my 1g trunk, which is more or less a sedan. It's all about how you build the box, what's stopping the sound from coming in (if at all) and how to remedy that. Half the time, you can use the rear speaker holes as vents, as you don't even need them.