Weak link

It would be really helpful if you created a virtual system and put some photos from different perspectives and of the components. This gives us a lot more to work on. Just a list of components is much less informative. Sometimes, some simple things can have profound effects.

Just off the top of my head. Your system looks pretty well balanced. What is your power conditioner, do you have direct lines? These two would be the first thing I would look at. 

If room treatment of some sort is possible, I'd start there. 

weak link 1 = lack of subwoofers

Get a Elac Varro DS1000 and use the built-in calibration tool it comes with (very handy tool for all subwoofer noobs). 

weak link 2 = lack of power conditioner

Get a Niagara 3000 or 5000

+1 @knotscott I would spend some effort treating the room.  You have very nice components.  Room treatment is likely the best bang for the buck.  A pair of subs would be interesting as well.

To refrain others, without a budget, photographs, and a room description/dimensions it’s hard to make recommendation on your solid system.  I would address the following, in the order listed, for both will have a positive effect on SQ:

1:  Power quality.  A good conditioner like a Shunyata Denali or Everest, or an Audience Adept Response T series.  Then, if your home design permits without much construction cost, dedicated 20 amp power lines.  If possible, one for digital and one for amplification.  
2:  Room Treatment.