Gary,
What kind if head unit do you have?
Remember, if the source is bad you will never have good sound whatever you do.
How many speakers do you have and where are they mounted?
The center console, as originally placed on the E-Type, is the absolutely worse place to mount them.
As you will only hear one speaker, playing on “Mono” mode might indeed improve things.
Also I was never fond of coaxial speakers, they are always a compromise.
In theory:
Doors are the best placement for Mid-Bass, because you have a big box behind to amplify them, and it doesn’t matter if they blast your feet as bass are not directional.
Kick-panels are very convenient for Mid-Range, reason being that they will be the most equidistant to your ears (mids are very sensitive on this)
Tweeters should be as closer to ear level and as equidistant as possible.
Do you have a sub-woofer?
Did you take care that the low signal RCA cables to the Amp are not close at any other cables? They are very sensitive to interference.
Like everything, it’s a compromise, if you want good sound you might have to sacrifice originality.
Post some pictures of your installation, I might be able to give you some clues.
Here is my installation, albeit on a XJ that has much more room.