Update:
The new ports arrived.
New bass+ ports (I'll call them bass++, although they don't add more bass than bass+ or even bass= ports) and new ultra super extra high+ ports (high++ from now on).
Plugged them in immediately.
Jackpot.
For me at least, Jason hit bullseye now.
The midrange has come alive. Shirley Horn lives and a piano is a musical instrument again. Cymbals are now sparkling instead of sizzling.
I experimented a bit more with different combinations:
New high++ with new bass++: super. They sound warm now instead of dark.
Old high+ with new bass++: dead mids
New high++ with old bass+: dead mids
Rather exaggerated to make my point of what differences I perceive.
Conclusion: both the new bass port and the high port improve the midrange considerably (well, to my ears at least...)
It makes them (especially the midrange) come alive. Bass is strong and articulate, but not overwhelming, it does not interfere with the midrange now.
Midrange gained detail and air with the new treble port.
Two thumbs up!
Thanks very much to Jason for his extra time, patience and efforts.
People will see a BIG grin on my face now!