hispls 5,000+ posts
CarAudio.com Veteran
That range is really tough in a car any way you slice it and is generally done in concerts, stadiums or even a good home system with large cone full range drivers. You see people using these "PA" woofers in cars filling up the doors but IMO it never really works as well as you'd think it should. Honestly I'd think the absolute best option would be to get a trunk in the front type car, get a sub that can play up to 200-300hz or so well and rely on that range being mostly non-directional hoping that your other fronts can pull things apart for some stereo separation.Midbass and honestly lower mids period are pretty bad. The combination of the honestly mediocre Morel 6.5's and their location, plus the tiny sealed boxes they are in make it impossible to pull any performance out of them. I honestly don't have a solution for this.
My experience also shows that location/aiming can make or break your sound and I'd also agree that apart from sheer output the soundbar won't really deliver what you're after. Good luck, do please update if you put any of this stuff into practice!