FWIW, Bose speakers in automotive applications are engineered and tuned for whatever particular vehicle they are installed in, just as the Mark Levinson system is tuned just for the specific Lexus model. Because the interior environment of each vehicle body is different, simply putting Bose speakers in your ES will not make it sound like your old Maxima. I think the ML system is outstanding personally, but I guess that is just my prefernce. My guess is that it will not be as easy as swapping one speaker for another because of the electronics behind both the Bose and ML systems.
I know this is a dumb question but, have to tried adjusting the tone controls and such for your system?
Just as a note of disclosure, I am not a fan of Bose products, but I do think their automotive applications are pretty good, especially in the Maxima. However, I think the Levinson system is a cut above.