Thanks so much for the great thoughts guys, and my apologies for taking so long to respond...
I ended up buying a 2018 Range Rover Sport Td6 (certified) and turned in the LR4 to a local Carmax for $3,800 cash. Definitely miss the LR4 already - such a workhorse, and a true member of our family!
I've already put 2.5k miles on the RRS. On one 1,000 mile trip continuous driving trip (yesterday actually), I averaged 28.4 mpg at 78mph. The diesel is perfect, and meets my needs of a DD/toy puller. I get my adrenaline fix from my track-ready GT3s (one PDK and one manual), so no need for anything crazy with the street SUV.
Of note, USED CAR PRICES are insane right now for mid to high end cars! I'd say that most of the Rovers are $10K above fair market value, and it has been that way since April (tax refunds?). I wanted to buy another RR Td6, but that would have put me about $10-15k above my budget...
Enjoy your LR4. It's my favorite Rover of all time. Wish the Disco 5 wasn't such a departure from the "spartan" roots.
-B