where best to spend $2-3000 upgrade dollars in my system

Can you identify that which you are unsatisfied with? If so please let us know so that the collective can better guide you in your quest.
You have what appears to be a decent system. 
There are many ways to throw money at an audio system. Many are misguided.
Don't try and fix something that isn't broken.  

Having owned Cornwalls twice in my audio journey, I agree that they like to be played at more realistic (live) levels, where they really come to life.
So many variables to take into account before any change. For instance, How large is your room? How close do you sit to your speakers? Concerns of noise transmission to other living spaces? Type of music most often played? ETC.
Room and speakers and the interplay between the two are THE most important aspect in an audio system. 
As has been mentioned, have you any acoustical treatments in your room?
Always a good place to start.

Now that you have listed the room size, I can better understand your statement concerning low listening levels. 
The Cornwalls would tend to dominate a space of that size and would be limited in their ability to perform at their best, not having sufficient breathing room.
It would seem to be a rather "live" space from your construction details. 
Room treatments are always a "best buy" as they will stay with you throughout and hardware changes.
If speakers are in your future, twoleftears has provided some good reccomendations. Also add Harbeth to that list. 
Might be worth while to look into standmounts/monitors for that size room.