Those crop up from time to time in ATL, which appears to be a decently strong wagon town.
There are about 14 RS6 Avants coming here to various Audi dealerships around town.
Edit: This one is still too young and pricey. But this is the dealer that seems to offer the best selection of used wagons:
https://www.autotrader.com/cars-for-...ckType=listing