I recall reading an net article that claimed without exception that full-range speaker drivers meant for autos tend to sound brighter. This is done to overcome the more absorptive accoustics of most cars and SUVs. Modern autos do have a more dead accoustics than typical homes. And they're mostly 4-ohms. So I guess it's up to your receivers if they can hande the lower impedance, and to your ears, ofcourse.