Have I Hit The Point Of Diminishing Returns?

+1 Doug Schroeder. Best of Luck

My listening room is nearly identical to yours and I recently tried something that made me sit up and say whoa.
I set my system in a diagonal configuration after reading this. The increase in soundstage depth alone was worth the effort. But honestly, as far as I can tell there were improvements in every sonic attribute of the system. And yes, my room has significant treatment going on.
If your system is movable you really should give it a try. I'm usually not much of a fanatic but I am a convert and am spreading the word.

Rlb61,
You've gotten two very different perspectives from Jmcgrogan2 and Doug Schroder. You specifically state that your system sounds "great". If it does truly sound that satisfying for you then John's comments are more applicable in your situation. It would make sense to avoid the High End merry go round and upgrade mentality. Expand your music library and continue to enjoy the great sound you've achieved. What is the goal or target if you do decide to upgrade from what's already great sound?
Charles,

I agree with John and Charles. In this hobby the word "dated" is irrelevant. Just listen to some great vintage gear

What John says is true, but if a particular switch or upgrade is worth it to you then that is all that matters.