Total replacement

Based on the cars you have owned previously, it appears that you like upscale (Acura, Lexus), sporty (Acura/Honda) and comfy (Avalon) cars. One car that comes to mind that I think you might like is the 2012-present Hyundai Azera. It is larger and more distinctive/attractive-looking than the Sonata, very comfortable (competes with Impala, Avalon, Taurus) and has fairy strong performance from a 293hp 3.3L V6. You should be able to find a 2012 and possibly a 2013 for under $20k. I've retned these on several occasions and I would have no problem buying one. They're great cars that get easily overlooked being stuck between the Sonata and Genesis in terms of size, class and price.

Another possible alternative is the Nissan Maxima. You can find 2014 models for $20k or a little less if you're willing to search. They're attractive, comfortable, strong performers and you don't see a dozen of them every time you go out.

It sounds like you'd prefer a car smaller than the current ES, which would rule out the Azera and Maxima.

Semi-premium cars that are smaller include the Acura TSX and Buick Verano. The latter might be less upscale than you want or not have all of the features you want, but worth a look.

The G37 might be too firm. But maybe not. And the price is often attractive. I agree it's worth a look.