My recommendation is to take part of your upgrade budget and a couple days of PTO and attend AXPONA this winter. This will help you calibrate your expectations by hearing other systems. You will get a chance to hear a wide range of speakers and electronics but most important it will give you a good sense of how your system stacks up to the current state of the art. Besides, it's just plain fun to geek out on this hobby for 3 days.
My guess is that you will conclude that your system sounds pretty damn good. That was certainly the case with me. I heard many rooms where the value of the cords, cables, and interconnects exceeded the value of my entire system and the whole thing didn't sound as good as my setup. I also heard other rooms that sounded gorgeous and it helped me better determine where my system could use improvement.
You have a very difficult upgrade situation because you are starting from such a solid platform. It's a good problem to have.