Am I done yet? LOL

You're never done.  My experience is that you bring in a new component that is of a much higher caliber than the rest of your system and the cycle begins anew.  Look on the bright side, if you sell off or trade in what you have, you have the makings of nice secondary system.

That's a good sign when your wife get engrossed in the music.  My wife does that as well.

I honestly think that I'm at a pretty good stopping point.  I like the way my system sounds and I think any improvements would be very tiny and very expensive. 

The amount of money one can dump into an audio system can become a bottomless pit!!!  The question is, how deep are your pockets Lol!!!  Happy listening.    

It sounds really good, but could use some more bass weight. 
During my speaker auditions, I had a pair of MoFi 888 speakers here and the bass was incredible....but that was all I liked about them. I could use some more of that. 

I do have a SVS SB-5000 R|Evolution sub, which is great for the very lowest bass, but I'm thinking about a second smaller sub or maybe an amp with better bass performance?

Nice system. Very clearly well thought out. Having your wife pleased is really a great endorsement. Women have much better hearing and are extremely sensitive to very low levels of high frequency hash and any distortion in the treble. If you are not careful you can put together a very high end system that will drive women up the wall... and not in a good way. So this is a great endorsement. 

So, I' recommend treading very carefully lest you loose that. I recommend doing a lot of listening to better preamps and amps. I would recommend Audio Research, Conrad Johnson, and VAC. These will elevate the level of details and realism without introducing a hard  or brittle high end. I would bring them home before buying and make sure your wife feels the same way. 

My partner finally loved the sound of my system when I moved to Audio Research... before that the same thing... that sounds very nice... and left.