Mate I'm aware of your angle

I wanted to clarify what
I meant when I was referring to flat frequency response in cars being , shall we say, "a tad unlikely...." ??

truly, even mega bucks systems, with 2 or 3 way active cross overs and individual monobloc amps per driver , even if running with an external mains supply , are still massively at the mercy of the acoustic space...
Kev, you can hear finer detail in a better controlled room , at lower levels.... think on that as a means to enjoy the music, and balance the wife's demands for peace and quiet.
The words you need to look up are.
Bass trap. (see also, Room modes )
First reflection point.
broadband absorption.
Boundary effect.
.
then there's the question of appropriate speaker and listener positioning.... quick guide...
listening position in the middle laterally, 38% of the longitudinal measurement in to the room.
you should form an equilateral triangle with the speakers, with the tweeters at ear height when listening.
angled in towards you, but , not at the middle of your head... a straight line should be drawn from tweeter dome to earlobe.
generally, for speaker position, some distance from the wall is also required,1-2 feet is usually adequate. unless the manufacturer specifically states the speakers are designed to work within the room boundary layer and need to be set there for Lf reinforcement.
there's more..... a LOT more to it, but there's enough to look up there to keep anyone busy for some time.... Remind me some time & I'll have to demonstrate for you mate.
Max